Kryptonite's Keeper Standard U-lock weighs a backpack-friendly 2.05 lbs. It also features a side mount, SNAP-IN BRACKET allowing you to keep it out of your pack and mounted to your bike. Rating a 5/10 on their security scale. Plus it's backed by Kryptonite's $500 anti-bike-theft guarantee.
Features
12mm HARDENED STEEL SHACKLE
NEW HARDENED DEADBOLT anti-rotation design.
Includes 2 STAINLESS STEEL KEYS, with ergonomic design to reduce the amount of torque, and keep them from bending or breaking.