Are there rack or fender mounts?
Bought a couple of these for me and my kids so that we could ride our bikes more. We live in a pretty low-theft town, so I can't testify to its durability, but it looks pretty solid. It looks like the kind of round lock that can be picked iwth a Bic - wouldn't use it in downtown NYC, but most other places where there are unlocked bikes on the racks it's probably going to be fine.
The lock is well-made and pretty nicely finished. There aren't any real edges on the lock, so it slides in and out of a backpack really easily. There's a slide over the locking mechanism. The slide isn't watertight, but it keeps lint and other gunk from the bottom a bag from getting into the lock mechanism.