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Master Lock

Master Lock 8170D, 6-1/8 inch Wide U-Lock with 8" Shackle, Black

  • Based on 4,976 reviews
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Availability: Only 1 left in stock, order soon!
Fulfilled by Prized Possessions Inc
Arrives Feb 18 – Feb 24
Order within 32 minutes
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Size: 6-1/8 inch U-Lock


Style: Lock


Features

  • Outdoor heavy duty bike U-lock is best used as a bicycle lock.Note: Measure your door's backset, cross bore and thickness to ensure you find the right fit.
  • U-shaped steel bike lock with key; Includes carrier bracket for easy transportation
  • Bike lock features a hardened steel body and double locking shackle for superior cutting and prying resistance
  • Bike lock body is 6-1/8 in. (16 cm) wide, with 8 in. (20 cm) shackle length, 4 in. (10 cm) width and 1/2 in. (13 mm) diameter
  • Includes one u-lock bike lock, two keys

Description

The Master Lock U-Lock is engineered for those who value their ride. This bicycle lock offers unparalleled security to ensure your bike stays right where you left it. It is crafted from hardened steel that can withstand significant impacts and resist all manner of attempts at tampering or cutting. This makes it an exceptional choice among bike locks for anyone serious about anti-theft security. The bike lock body is 6-1/8-inches wide with an 8-inch shackle length. Whether you are locking up your bicycle in a bustling urban environment or a quieter suburban area, trust that this heavy-duty bike lock has you covered. Its imposing presence alone deters would-be thieves before they even think about attempting anything nefarious. But what sets this U-lock bike apart from others? The answer lies in its intuitive design and ease of use. Despite its strength and durability, the Master Lock 8170D U-Lock is incredibly user-friendly. It boasts a double-locking mechanism providing twice the security while ensuring quick access when you need to unlock it swiftly. Lightweight yet sturdy, this U-lock fits easily into most backpacks or bike accessory bags without weighing you down. Investing in the Master Lock U-Lock means investing in long-term security for your precious ride. Unlock superior protection now with Master Lock: where studied design meets impenetrable strength.

Brand: Master Lock


Special Feature: Heavy Duty


Lock Type: Key Lock


Item dimensions L x W x H: 9.8 x 7.33 x 1.33 inches


Material: Alloy Steel, Rubber


Brand: ‎Master Lock


Special Feature: ‎Heavy Duty


Lock Type: ‎Key Lock


Item dimensions L x W x H: ‎9.8 x 7.33 x 1.33 inches


Material: ‎Alloy Steel, Rubber


Recommended Uses For Product: ‎Bike


Style: ‎Lock


Color: ‎Black


Number of Pieces: ‎1


Finish Type: ‎Vinyl Coating


Included Components: ‎U-lock bike lock, two keys, and a carrier bracket


Controller Type: ‎Hand Control


Shape: ‎U Shape


Item Weight: ‎1.96 Pounds


Control Method: ‎Touch


UPC: ‎071649222771


Model Name: ‎8170D


Global Trade Identification Number: ‎71


Manufacturer: ‎Master Lock


Part Number: ‎8170D


Item Weight: ‎1.96 pounds


Product Dimensions: ‎9.8 x 7.33 x 1.33 inches


Item model number: ‎8170D


Is Discontinued By Manufacturer: ‎No


Size: ‎6-1/8 inch U-Lock


Finish: ‎Vinyl Coating


Item Package Quantity: ‎1


Special Features: ‎Heavy Duty


Batteries Included?: ‎No


Batteries Required?: ‎No


Warranty Description: ‎Limited Lifetime Warranty


Date First Available: April 9, 2008


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Feb 18 – Feb 24

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.

  • Klarna Financing
  • Affirm Pay in 4
  • Affirm Financing
  • Afterpay Financing
  • PayTomorrow Financing
  • Financing through Apple Pay
Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

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Top Amazon Reviews

    • Exellence
Size: 7-1/4 inch U-Lock Style: Lock
Review Image by Ashley Shook Ashley Shook
Absolutely love this lock, the thickness gives me ease of mind. Quality is tip top especially for the price you pay for it. Comes with keys and holder for your bike that you can install. The bar unlocks from both sides making it very easy to install and unlock your bike from racks.
Reviewed in the United States on December 31, 2025 by Ashley Shook Ashley Shook
    • These are really nice for the price
Size: 7-1/4 inch U-Lock Style: Lock + Cable
Review Image by Russell Russell
Review Image by Russell Russell
These locks are nice and sturdy the cable is really thick and the mounting brackets are pretty easy to install
Reviewed in the United States on December 6, 2025 by Russell Russell
    • Excellent lock....
Size: 6-1/8 inch U-Lock Style: Lock
The lock works great. Real easy to use.
Reviewed in the United States on December 16, 2025 by Robert Burgo
    • Strong, Reliable, and Perfect for Everyday Bike Security
Size: 7-1/4 inch U-Lock Style: Lock + Cable
Strong, Reliable, and Perfect for Everyday Bike Security This Master Lock U-Lock with the 4-foot cable is one of those dependable tools that just works as advertised. I’ve been using it for both my e-bike and a standard mountain bike, and it gives a solid sense of security without being overly heavy or bulky. The steel shackle feels tough, and the lock engages cleanly every time. The included cable is a nice touch—it allows you to loop through the front wheel or seat so you’re not leaving easy targets for opportunistic theft. The keys fit snugly, and the locking mechanism operates smoothly without any jamming, even after exposure to morning dew and coastal humidity. The included mounting bracket makes it easy to keep on the bike frame for quick access, and the lock’s size is just right for most bike racks and poles. While this isn’t meant to stop a professional with power tools, for everyday use—like parking at cafes, parks, or college campuses—it offers a great balance of strength, convenience, and price. Bottom line: A sturdy, well-designed lock-and-cable combo that provides trustworthy protection for daily riders at a very fair price. ... show more
Reviewed in the United States on October 26, 2025 by Everyday Reviews
    • Secure lock to prevent theft!
Size: 6-1/8 inch U-Lock Style: Lock
Great lock. Needed it for my scooter and never failed me once over 1 year of use. Couple of my friends had a wire lock and their scooters unfortunately got stolen. The lock is very durable, and it comfortably fit around my scooter with no struggle. Also, had to ship the lock across the country in the same box as the scooter and it did get banged up a bit with visible scratches but it didn't affect the durability at all! Ended up forgetting my key at times too, but luckily they give a backup key! Only concern would be that the key is annoying to use sometimes, but never bothered me in any significant way. Definitely recommend. ... show more
Reviewed in the United States on September 26, 2025 by Mr. Beast
    • Sturdy & Convenient
Size: 7-1/4 inch U-Lock Style: Lock
Review Image by seb seb
This U-Lock came with a mounting bracket as-well, which was able to be used on the handlebars of my electric scooter. It’s not too heavy and comes with a pair of keys attached. It seems pretty solid, and so far hasn’t made much noise when moved! The U-bar has just enough space where it can accommodate a bike rack of many sizes. ... show more
Reviewed in the United States on February 1, 2026 by seb seb
    • Excellent Lock!
Size: 7-1/4 inch U-Lock Style: Lock + Cable
Perfect lock! Works great, easy to unlock and very sturdy! Will fit both big and small tires or any part of your bike, or whatever you would like to lock up.
Reviewed in the United States on October 19, 2025 by Amazon Customer
    • Solid for the price
Size: 7-1/4 inch U-Lock Style: Lock
For the price it's a pretty decent U lock
Reviewed in the United States on January 28, 2026 by Frank

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