Locks that work

Its supposed to be 18mm, but I'd trust the Parker International version rather than the Amazon sale. They're some fake Kryptonites on the market, and I think I'd steer clear of something that just looks wrong.

Someone on here bought what I feel is a fake Kryptonite chain, and its probably not such an isolated incident. Buyer beware.

A lot of people get confused with the M18 as it's so similar in appearance to the 16mm NY. It's actually classed by Kryptonite as a powersports product (i.e. motorbike lock) so you won't find it listed under bicycle category locks on their website...
https://www.kryptonitelock.com/Products/ProductDetail.aspx?cid=1000&scid=1000&pid=1093

Madison (UK Krypto dist.) have been bringing it in and selling successfully in the bicycle market for a good few years as it gives gives more room to maneuver than the 18mm Fahg. Bloody heavy mind!

Hope this helps.