The Yakima SKS Lock Cores 4-Pack is a simple solution to locking four of your Yakima racks and accessories with a single key for maximum convenience. Simply pop out the pre-existing lock core that came with your Yakima rack and install these interchangeable cores. This four-pack of SKS cores comes with two master keys, just in case you happen to misplace or lose one. It also includes a control key that removes existing unlocked cores, so you can swap in new locking cores.