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ONGUARD

OnGuard Mastiff 3.5 ft Chain Lock with Integrated Key Lock – 10 mm Hardened Steel Hex Links (110 cm / 3.57 ft) – X2P Double Bolt Lock Head, Z-Cylinder Core, 5 Keys

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Availability: Only 5 left in stock, order soon!
Fulfilled by Amazon
Arrives Monday, May 4
Order within 3 hours and 44 minutes
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Size: 10mm x 3.5 ft


Features

  • High-Security X2P Lock Head: Integrated X2P Double Bolt mechanism locks both sides for superior resistance against pulling, twisting, and prying attacks.
  • Heavy-Duty 10 mm Steel Chain: Titanium-reinforced hardened steel hex links provide strong defense against cutting, leverage, and impact attacks.
  • Practical 110 cm Locking Length: 110 cm (3.57 ft) chain length provides flexible locking options around racks, poles, and fixed urban objects.
  • Advanced Z-Cylinder Protection: Precision locking core resists bumping, drilling, and picking for dependable anti-theft performance.
  • Complete Key Set Included: Comes with five laser-cut keys.

Description

The OnGuard Mastiff 3.5 ft Chain Lock delivers serious protection for bikes, scooters, and e-bikes in medium-to-high risk environments. The 110 cm (3.57 ft) chain is built with titanium-reinforced hardened steel hex links designed to resist cutting, prying, and leverage attacks. The chain integrates directly into a heavy-duty X2P Double Bolt Lock Head, securing both sides of the locking mechanism for exceptional pull resistance. A dual rubber housing helps protect frames and finishes from scratches while also improving durability and weather resistance. The advanced Z-Cylinder core adds protection against bumping, drilling, and picking attempts for dependable long-term security. Designed for riders who want strong yet manageable protection, this chain lock offers an ideal balance of durability, portability, and everyday convenience. Includes five precision laser-cut keys.

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 Name: ONGUARD


Recommended Uses For Product: Cycling, Security


Included Components: ONGUARD 8020


Model Number: 45008020


UPC: 768661281328 768661280208


Global Trade Identification Number: 08


Manufacturer: OnGuard


Item Type Name: Bike Lock


Unit Count: 1.0 Count


Manufacturer Warranty Description: 2 year manufacturer


Additional Features: Heavy Duty


Lock Type: Key Lock


Controller Type: Hand Control


Control Method: App


Style Name: Modern


Color: Black


Shape: Square


Material Type: Rubber


Finish Types: Painted


Item Dimensions: 11.5 x 8 x 3 inches


Item Weight: 5.7 Pounds


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Monday, May 4

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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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
    • Quality
Size: 10mm x 3.5 ft
Great lock very hard to cut even with 4 feet bolt cutters
Reviewed in the United States on February 21, 2026 by David Bobrink
    • 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
    • A great chain to protect 1 bicycle.
Awesome chain. It will delay potential bike thieves much longer than most cables/wires that are on the market. Its heavy fabric outer covering protects my car's roof from scratching. It comes with 4 keys, too, unlike some other famous companies that give you 2 keys, and then charge exorbitant fees for additional keys/lock heads. (Yakima can you read this please.) I have a 2-bike roof rack system, and I will buy a 2nd Mastiff to protect another bicycle. The chain is very heavy and not long enough to securely protect 2 bikes, however, it will secure 1 bike. ... show more
Reviewed in the United States on May 27, 2016 by 12 sunyata
    • 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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