There's little doubt that bicycle thieves are deterred more by U-locks than by cable locks. The form factor of U-locks, however, can make them awkward to transport. That's why California cyclists Allen and Paige Young have created the Vier lock. It's designed to offer the security of a U, but it disassembles into a package "the size of a burrito" when not in use.
The Vier consists of two cylindrical locking bodies and two 14 mm-thick shackle sections, all of which are made of vinyl-covered hardened steel. Plans call for the shackles to be available in three lengths, to accommodate different sizes and styles of bike frames.
When it's time to lock up, the shackles are just inserted into the locking bodies, then a single key is used in a pick- and drill-resistant lock cylinder located in one of those bodies. Once everything is locked together, the Vier has a reported 1.5 tons (1.36 tonnes) of pull strength.
After the lock is taken back apart for transport, it's stuffed into an included zippered pouch that can be mounted under the saddle using an integrated strap.
Allen and Paige are now raising production funds for the Vier lock, on Kickstarter. A pledge of US$65 will currently get you one, when and if they're ready to go. The planned retail price is $80.