Matthew Syringwrote a review of Yakima SKS Lock Cores - 6 pack on January 4, 2018
Familiarity: I've used it several times
Paired with Yakima Fatcat 6, Yakima Timberline Towers, and Yakima Corebar on a 2010 Subaru Forester. They work, they lock, only thing is I wish that they were better quality in general. They kinda feel like dinky little things that'd come in a cereal box. I think this is the exact same lock design Yakima has used since the 80s.
Other than that, they work great. Definitely a necessity to go with your Yakima products.