I have a Kryptonite New York STD U-lock. I believe it weighs 4.3lbs, maybe 4.2. Initially I got the NY FU U-lock, but I found that its small size made it less adaptable to different locking situations. If I'm going to carry around a 4lb lock, I want to make sure it's useful. The NY STD is bigger, and slightly lighter than the FU, and I feel pretty safe with it. Because I like the convenience of a small lock, I also have an Abus Granite Futura 64, mini U-lock. It's incredibly light, and I've been pretty happy with it, though I generally use it for shorter periods when I'm not far from my bike. It's lighter, narrower, and a little longer than the Kryptonite Evo Mini. The NY FU lock is a beast (no OnGuard pun intended) though. I was impressed with how thick & heavy it is. If I was a bike thief, I'd tend to avoid that lock if I had other options- which I would, thanks to everyone else using cable locks.