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ONGUARD

OnGuard 8020 Mastiff Integrated Key Chain Lock - 3.57' X 0.39"[110CM X 10MM] Black

  • Based on 508 reviews
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Availability: Only 5 left in stock, order soon!
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Arrives Wednesday, Feb 25
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Size: 10mm x 3.5 ft


Features

  • High-Security X2P Head: Integrated X2P Double Bolt Lock Head provides extreme pull resistance and features a dual rubber housing for added impact and weather protection.
  • Heavy-Duty Steel Chain: 1090 mm chain made from 10 mm hardened-steel hex links delivers superior cut, pry, and leverage attack resistance for confident daily protection. Weighs 5.7 pounds.
  • Built for Riskier Areas: Ideal for medium-to-high threat environments, offering reliable defense for bikes, e-bikes, scooters, and motorcycles during everyday use.
  • Advanced Z-Cylinder Core: Precision-engineered locking cylinder resists drilling, bumping, and picking, ensuring long-term reliability and theft prevention.
  • Includes Five Keys: Comes with five laser-cut keysincluding one LED keyoffering smooth operation and excellent visibility for night-time use.

Description

The OnGuard Mastiff 3.5 ft Chain Lock is built for serious security in medium- to-high risk areas. Its 1090 mm (42.9 in) titanium-reinforced hardened-steel hex chain integrates directly into an X2P Double Bolt Lock Head for exceptional pull resistance. The advanced Z-Cylinder protects against bumping, drilling, and picking, while the dual rubber housing shields paint and finishes. Perfect for bikes, scooters, and e-bikes, this lock balances strength, durability, and ease of use. Includes five laser-cut keys, one with an LED light. Weighs 5.7 pounds.

Brand: ONGUARD


Special Feature: Heavy Duty


Lock Type: Key Lock


Item dimensions L x W x H: 11.5 x 8 x 3 inches


Material: Rubber


Brand: ‎ONGUARD


Special Feature: ‎Heavy Duty


Lock Type: ‎Key Lock


Item dimensions L x W x H: ‎11.5 x 8 x 3 inches


Material: ‎Rubber


Recommended Uses For Product: ‎Security, Cycling


Style: ‎Modern


Color: ‎Black


Number of Pieces: ‎1


Finish Type: ‎Painted


Included Components: ‎ONGUARD 8020


Controller Type: ‎Hand Control


Shape: ‎Square


Item Weight: ‎5.7 Pounds


Control Method: ‎App


UPC: ‎768661281328 768661280208


Model Name: ‎45008020


Global Trade Identification Number: ‎08


Manufacturer: ‎OnGuard


Item Weight: ‎5.7 pounds


Product Dimensions: ‎11.5 x 8 x 3 inches


Item model number: ‎8020


Is Discontinued By Manufacturer: ‎No


Exterior: ‎Painted


Manufacturer Part Number: ‎8020


Special Features: ‎Heavy Duty


Date First Available: November 17, 2011


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Wednesday, Feb 25

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

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Similar Products

Top Amazon Reviews

    • Really solid lock.
Size: 6' x 3/8""
A touch heavy, still a great lock. LOVE the extra length. I carry mine in a basket so the weight does not bother me.
Reviewed in the United States on December 23, 2025 by Amazon Customer
    • Heavy duty and just plain heavy! But very secure!
Size: 6' x 3/8""
Like carrying a tow chain. I will only use this when my bike needs to be left outdoors. Not something you’ll carry on a ride. But, it’s what I expected and definitely serves its purpose. Don’t buy it if you are expecting it to be light.
Reviewed in the United States on July 2, 2025 by Mike Tucson
    • Heavy chain, scary padlock!
Size: 6' x 3/8""
The 10mm chain is substantial. The padlock size took me aback when I first unwrapped it. The lock mechanism is smooth and easy to use. I like that the lock has a rubber coating on the U portion. I was somewhat surprised by the amount of plastic sheathing on the lock, but it does appear sturdy. I bought an OKC noose chain to go with (my Scouting unit often goes on group rides to the movies, etc., so this extends the group coverage while we're inside). The OKC links are narrower, but do slide over the lock (displacing some of the rubber coating). The OnGuard chain is robust. I could slide the nice cover enough to check all the link welds which looked good. Hoping to get many an event-free year with this lock and chain. Nothing will deter a determined thief, but this will at least divert attention elsewhere. When we go away, the lock and chains are used to secure our bikes to the floor anchor. ... show more
Reviewed in the United States on July 23, 2023 by KCCjr
    • Solid. Bulky solid. Legit.
Size: 10mm x 3.5 ft
This lock is no joke. The chain is heavy and there is no denying that. The lock is a bit silly in my opinion. The key doesn’t easily slide in and it’s very ambiguous as to whether it’s locked or not (click feel when turning key). The key doesn’t come out when it’s unlocked - which is very clear - but I would rather have a more traditional @click - it’s locked” type of feel. ... show more
Reviewed in the United States on April 14, 2024 by Nathaniel P Molgren
    • Heavy but hardcore good
Size: 10mm x 3.5 ft
Great lock. Only reason i gave 4/5 is because it’s very heavy. Which means secure? Lock and keys work very smoothly and its big enough to both protect your bike or yourself:)
Reviewed in the United States on November 19, 2025 by Jbird
    • Awesome, super heavy duty lock and chain
Size: 6' x 3/8""
I've had this for several years and LOVE it! When I have to leave my bike on my rack in truck I leave this on it and feel 100 secure cause it's a huge beast. It's REALLY heavy and it is awkward but it's worth it to know it's locked up safe. I spent hours reviewing bike locks and chains before buying this and a big time review in NYC couldn't get through it even with battery powered tools. And it's not even expensive considering what it is. ... show more
Reviewed in the United States on November 29, 2018 by Seth
    • Great lock ,
Size: 6' x 3/8""
Great lock, however way to heavy 10 pounds for the weight of this bike lock.
Reviewed in the United States on June 15, 2025 by Don
    • So easy and quick to use!
Size: 10mm x 3.5 ft
I struggled to figure out how to use this the first time, because I thought there was a trick to turning the lock and removing the key. There’s no trick. Basically if the key is in the lock the lock opens. You can’t remove the key unless you lock it again. This is a rather genius way of making sure you don’t lose your key. Now that I understand it, it’s super simple to tie my bike up anywhere in just a few seconds. The chain is heavy duty, so this is not a fun thing to carry around (heavy). I keep it in a pannier on my bike, so it never really bothers me. Another option is to wrap it around the top tube several times and lock it in place while on the go. No need to keep it in a backpack. I got the smaller size, and that's more than enough length for securing my bike everywhere I go (unless you are tying it to a tree). It's a rather menacing looking lock, so unless someone is traveling with a saw, your bike isn't likely to become a target. I was tempted to buy some of the cheaper options, but I am SO SO glad I went with this one. I feel very confident about my bike being secure wherever I leave it. Definitely worth the money. ... show more
Reviewed in the United States on November 10, 2024 by Faith H.

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