Need a little extra security in a bike lock? Move along. Need maximum security in compact U-Lock, one rated at 10/10 on the security scale? Then you are looking at the right lock. The RockyMounts Compton Large U-Lock may be the toughest such lock ever made for consumer applications. The 18mm stainless steel shackle is the largest and toughest available on market, just ask it. The shackle is CNC machined, from non-corrosive 304 stainless steel, which even in much smaller sections is very difficult to cut. Stainless steel is very hard on tools, even stainless-specific versions, and compromising it means serious tools, time, and desire.
The Compton Large was developed for serious security in urban environments. This design is ideal for expensive bikes that get locked up in the city for hours at a time. RockyMounts supplies three keys, so you have no excuse for being locked out, as it were. But seriously, if you live in the city and have a valued bike, regardless of what is actually worth, you need to invest in the RockyMounts Compton Large U-Lock.