Mark Traverswrote a review of Thule Lock Cylinders on October 23, 2015
Familiarity: I've put it through the wringer
These are ok, but wish they were not as expensive / included when you buy a roof rack. They've worked fine for me and I haven't had any issues with these seizing up, even after being caked in road salt in the winter. If you end up needing more locks than you bought in the first round, you can get extra locks directly from Thule that match the keys you already have, which is a nice touch. Also, if you lose a key or a lock cylinder you can get replacements from Thule as long as you have the number stamped on the key.
These things work fine and do exactly what they're supposed, just kind of a bummer that they aren't cheaper