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Mongoose

Mongoose Legion Kids Freestyle BMX Bike

Based on 2,149 reviews
Condition: New
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$279.99
Holiday Deal · 10% off was $309.99

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Availability: In Stock.
Fulfilled by Amazon
Arrives Tuesday, Nov 17
Order within 1 hour and 56 minutes

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At a glance

Condition
New
Size
20-in Wheels/L20
Color
Black
Model
M4146G27U2OS11
Weight
28.6 lb
Material
High Tensile Steel
Bike Type
BMX Bike, Kids Bike
In the box
ReflectorsUser Manual
Warranty
Limited lifetime warranty on frame. 1 year limited warranty on parts. 30 day limited warranty on wearable parts.

Features 5

  • STEP UP YOUR GAME: Built for riders 5' 3" to 6' 0" tall who are progressing beyond the basics, this 20-inch freestyle BMX bike delivers upgraded components for park, street, and everyday riding.
  • CONFIDENT GRIP: Wide 2.3-inch tires provide confident traction on pavement, park surfaces, and packed dirt. Built to help riders stay planted while building skills and trying something new.
  • POWER THROUGH THE SESSION: A lightweight 3-piece chromoly crank delivers reliable power transfer and the durability riders need when tricks, jumps, and ride time start getting more serious.
  • UPGRADED WHERE IT COUNTS: A 9T sealed rear hub supports smooth rolling performance, while a 14 mm axle adds durability to handle repeated landings and everyday BMX abuse.

Specs 33

Bike Type BMX Bike, Kids Bike
Age Range (Description) Youth
Brand Mongoose
Number of Speeds 1
Color Black
Wheel Size 20 inches
Frame Material High Tensile Steel
Suspension Type Rigid

Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Tuesday, Nov 17

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

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View our full returns policy here.

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Top Amazon Reviews

Yes! Mongoose is back to the good stuff!!!
Size: 20-Inch Wheels/L60 Color: Green
Just get one. This is Mongoose like in the 80's and early 90's. Not the junk crap that Walmart and other department stores still sell. Avoid those like the plague! But then, that's apparent to any real BMX rider. Those are all flash for what little you pay and no real quality. If you already have one of those, strip it down to the bare frame and only the frame and build everything else up from scratch. That's those bikes only hope. This on the other hand is fine the way it comes. Ok, may have to make a few tweaks and whatnot along the way, but that's to be expected of even the best BMX bikes. It's part of riding and making it your own. I do wish they'd have given it at least a somewhat taller seat post, and I'm also not crazy about how the seat is permanently attached to the seat post as well. Normal seat and seat post setup is, if the seat wears out or isn't to your liking, you can just stick a new seat on the seat post. Here, you have to replace both. Was expecting something like a pivoting seat post or perhaps the old bolt down kind. On the other hand, the seat that's here, by BMX standards, is plenty acceptable until I upgrade. I got the L60 and I'm not sure it mentions it in the details, but it appears as though it's sporting a rear wheel that's sealed while the front wheel is not sealed. But the L60 is totally the midrange offering of the whole Legion lineup. So it's expected that a few things are somewhat average, besides, the rear wheel is where you want and need a better quality one at, uh, if you're going to cut corners that is. Also, contrary to what I'm seeing in other reviews here, the brakes do work surprisingly well. More than adequate. The bike arrived perfectly and overall inspection found one very minor blemish. Top tube on left side has like a weird smudge in the paint job that then glossed over for it's final painting. I tried Goo Gone thinking it might have just been grease, it's kind of a blackish color against green giving that effect sorta, but after a good rubbing it remains unchanged, so I can tell it's permanently on there. Both very minor and totally cosmetic, a classic error no doubt the result of being mass produced. Everything else is brilliant here plus I caught a sweet sale on mine and got it for only $146.87 + tax. Arrived quickly, packaged well, everything is in perfect condition, so yeah, I'll excuse one little minor smudge. Thank you Mongoose!!!! ... show more
Reviewed in the United States on May 2, 2023 by Matt Jacoby
Good bike for the money
Size: 20-Inch Wheels/L20 Color: Red
All you need are some tools, a brain, some patience and reasonable expectations for this to be put together and on the road. If you have half a brain and basic tools, you’re going to be able to put this together without even looking at the instructions. This will come in a box, front tire packaged off. It comes with no tools, everything zip tied so it could remain intact on the long trip from CHIIIINA to the US. Packaging is solid. There are several thick zip ties to cut to break everything loose. You’re going to need: Metric hex tools A 15 and 18 mm socket for axels 15mm wrench or socket to tighten handlebar alignment Scissors or utility knife for zip ties Phillips screwdriver (for the reflectors only) You’ll need an extension bar to remove the nuts from the axels to install the pegs on front and back. Will take you about 60 seconds to do this. Front handlebars install with hex keys. Honestly not sure how anybody could have problems with this. It’s four bolts. Secure them, and you’re good. But man, some reviewers couldn’t figure this out. Install the seat with another hex socket. Put on the reflectors, hook up the brake, fill the tires with air, and you’re riding. Btw, the factory purposefully ships tires with less air than you’ll need for your benefit. Any tire sitting for an extended period will last longer if not fully inflated. Hooking up the brake is a bit of a pain in the A, as you won’t have enough slack in the front to properly attach the cable unless you briefly disconnect the rear brakes. Once you pull the cable through in the front to attach, reattach the rear. Took me a minute to figure this out. The front break setup is such that you can spin the handlebars around to 1) look cool, and 2) not have the brake line get wound around the front of the bike. The bike is good, solid and worth the money. Assembly, with any mechanical skill (even entry level mechanical skill) will take 20 minutes. Also, warning: you’re buying a $200 bike. It will last like a $200 bike. Many people on here complain about the quality. This isn’t a $1000 bike. Don’t pretend it is. Take care of it, don’t beat it to death and you’ll be good. If this was at all helpful, please hit the button. ... show more
Reviewed in the United States on December 21, 2020 by HolyShoot
Great quality bike and light weight
This Legion L20 is the third Mongoose BMX bike I've purchased over the last year, and I've been very happy with all three (Legion LSX, Title Pro, and L20). Assembly was very easy on all three bikes; just need to attach the front wheel, handle bars, and pedals. Took only about 15 mins. You just need to pay attention to the direction of the forks and remember the left pedal will be left-hand threaded. The forks and pedals have stickers denoting front/rear, left/right. Besides adjusting for height and putting air in the tires, there really wasn't any need for fine adjustments (chain tension, brakes, misc. nuts, etc.), as these things are being adjusted correctly from the factory (nice surprise). After reading the negative reviews on this bike and the others mentioned, it seems many of them are related to incorrect user assembly. If you put the forks on backwards or don't put air in the tire, you're going to have problems. The Legion L20 is reasonably light at roughly 25 lbs., easy to ride, and looks great. Note, however, that this is a freestyle bike, and probably not the best choice if you're just looking for a neighborhood cruiser. The crank bracket sits about 1" higher than on a race type BMX bike, making the apex pedal feel too high when in a sitting position. This may not bother some people. If it does, you could buy shorter cranks, but with the money you'd spend, it would be more logical to just go with a race style bike with the lower bracket (and larger front sprocket). The Title series with a lengthened seat post makes for a great lightweight cruiser. Not much to complain about on this bike. Excellent quality for the money. If you're looking for a reasonably priced freestyle bike with good quality, at $156, this is a great choice. ... show more
Reviewed in the United States on October 24, 2020 by Anonymous
Good Bike, Bad Assembly Manual
Size: 20-Inch Wheels/L20 Color: Red
< Overall > So first off, this is a decent bike. Having twin boys this has all the cool features that they didn't even know they looking for (that's because these were features I was looking for at their age); free wheel, spinny handlebars, foot pegs, and a cool color scheme. I've read some reviews of this bike on other, bike-oriented sites that pick apart certain mechanical aspects of this bike and I must say people sure seem to expect a lot for this price point. From my perspective--and having grown up with a Huffy--this is about the nicest bike I could imagine having as a kid. < Assembly > Having twin boys meant that I got to experience assembly twice. Which is the reason I deducted a star from the bike, the assembly manual is generic and meant to cover several versions of these bikes. As such it does every version of the bike a disservice by not actually explaining things very well or at all in the case of the brake cable installation for the L20. There isn't a lot to the assembly. The main frame and all the components are already installed. You just have to put on the front wheel, mount the handlebars to the stem, install the seat, pedals, foot pegs (if you even want them), and finally attach the brake cable to the brake lever. Having a metric socket set and Allen key set are essential. < ASSEMBLY NOTE: Attaching the Brake Cable > I've seen more than a few reviews here decrying the assembly of the brake cable with folks going so far as to return the bike, buy additional parts, or dump it off at the bike shop. Let me say I understand your struggle. However, I did figure out how to install the cable without needing to go that route and it was actually pretty easy. The cable, as it turns out, is the right length, but I found it necessary to disassemble the brake lever and remove it in order to make it work. I takes the 4mm allen key to remove the screw. The lever components include two plastic bushings on either side of the lever and a spring. Pay careful attention to how these parts come out, because reassembly is the same. Once the lever is off and the brake cable is fed through the lever mount, you can line up the cable and the barrel in the hole on the lever and rotate it into place. Now you'll actually have enough leverage to easily re-seat the lever arm although it will require a modicum of coordination to make sure all the parts stay on the arm until you can get them back into the handle-bar mount. I don't know if I explained that well, I'm not even sure if that was the easiest way to do this, but it worked reliably for me. < FINAL NOTE: Test! > Once everything is assembled, test the bike. I cannot stress this enough. Don't assume that because it's all been assembled it's ready to go. The manual itself makes a big point of this as well. ... show more
Reviewed in the United States on October 6, 2020 by Ajax
MNG Legion L20 (Red): Excellent Bike!
Size: 20-Inch Wheels/L20 Color: Red
Review Image by Amazon Customer
Review Image by Amazon Customer
Received the bike within a week. Assembly difficulty was medium-low. The instruction manual was more general for all Mongoose BMX bikes. The simple order of assembly was: handlebars, brake, seat, wheel, pedals, pegs, (F&R) reflectors. Previous reviews claimed the brake line was a pain to install. Found out the hard way was to install the line into the handbrake right before mounting the handlebar. After everything was installed, i inspected the bike and tightened as necessary. The axel nuts were different sizes in the front and rear and pegs were properly sized for each. The brakes did require adjusting. I used a Park Tool 4th Hand. The tires needed a little bit of air for the recommend 40 psi. Both tires out of box were in the 30s. My son had no problem with this bike. He is 10yo and about 4’9”. This was not his first hand brake so no issues there. His previous bike was an 18” with coasters and hand brakes. He said this bike seems heavy but rides very smoothly. His only complaint is the whistling from the hollow stem bolt while he rides. I have even taken his bike for a few spins and it’s the perfect size and weight for your basic tricks and jumps. I did add a children’s Bell adjustable kickstand but doesn’t appear to last much longer. We want the kickstand because he’s always parking in the garage by the cars and doesn’t like the bike just laying on its pegs. Any questions, please feel free. ... show more
Reviewed in the United States on May 31, 2020 by Amazon Customer
Best bike around. My 10 Yr Old loves it.. I used to BMX and better than my bikes.
Size: 20-Inch Wheels/L60 Color: Grey
This bike is Amazing. And even though I got it Used it came in Mint Condition still in the Box. Great Seller. My 10 Year old Daughter wanted a good Boys Bike and this one is outstanding. Much better than the Mongoose I had in 1984. I had to pull the handlebars back a little bit for her. Brakes are real good to compared to most that come on the bike. I think if you can get this for under $250. It's a steal. ... show more
Reviewed in the United States on September 23, 2025 by Joel
Very disappointed in this bike!
Review Image by Tina
We were excited to give this to our son for his 11th birthday, but the experience was frustrating from the start. After assembling the bike, one tire wouldn’t inflate, and we discovered a huge hole in the inner tube. After buying a replacement inner tube, we tried to ride—but the seat is completely uncomfortable, points awkwardly up in the groin, and doesn’t adjust for his height. When he finally got on the bike, the back tire then went flat, —again another hole in the tube. At that point, we had to disappoint our son and return the bike. I chose a Mongoose thinking it would be a reliable upgrade from the Walmart bikes giving him a few years on a "real" bike, but we didn’t even get a few hours. To make matters worse, it’s been over two weeks since we returned it, and we still haven’t received our refund. Amazon says we need to wait another 7–14 days because it’s a high-ticket item. Extremely disappointing all around. ... show more
Reviewed in the United States on August 16, 2025 by Tina
Nice bike for the money
Size: 20-Inch Wheels/L20 Color: Red
Came boxed in what I felt was a heavy duty box. No damage on arrival. Just had to put the wheels and bars/neck on it and it was ready to go. I know these aren’t the quality of the old mongoose I had growing up 40 years ago but I was impressed with it. Looks like a more expensive bike than it is. My 7 year old is tall for his age but I still wondered if it would be too big. Not at all. He loves it. He has a redline pro mini race bike and he would rather ride this one at home. We haven’t put a ton of time on it yet so can’t truly say how it will hold up. Only issue right away was back hand brake was so stiff that he couldn’t stop it. After looking at it the brackets for the shoes have tension that’s adjustable. So we were able to ease the effort up on the brake. Now it’s fine for him. As long as it doesn’t fall apart in the immediate future I would definitely buy it again ... show more
Reviewed in the United States on June 25, 2021 by Amazon Customer
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