D-Lock Size

A standard D-Lock will easily fit around your bike and normal bike racks. If you have a particularly wide framed bike you can get wider and longer shackles. Alternatively, there is also a range of mini D-Locks are that specifically for use just with a standard bike rack. You won’t be able to fit your bike around a lamppost with a mini.

For security, it is best to get a D-Lock which will fit your frame and stationary object without leaving too much internal space. A common way for thieves to defeat your D-Lock is by slipping another object like a crowbar inside the shackle and leveraging with enough force to break it open.

Lock Material

Almost all D Lock shackles and locking mechanisms are built out of steel. However, some locks will be constructed from hardened steel. By tempering steel if becomes harder and less brittle making it much tougher to cut through.

An approved lock is graded as Gold, Silver or Bronze. The rating is chosen by how long it takes to break the lock and the tools needed to break it. If you're planning on insuring your bike, many insurers will state you need a Sold Secure rated lock to make a successful claim.

These values vary between insurance providers so check the terms and conditions of your provider.