Compatibility The core locks perfectly fit and are compatible with all Thule products. Thule products use the same lock cylinder, such as bike racks, roof racks, ski racks, cargo boxes, cross bars, towers, kayak racks, and more. The package includes 4 lock cores, 2 keys, and 1 universal master key for adding or replacing lock cores. Built to Last The lock cylinders are made of high-quality aluminum alloy material. The inner core is made of brass. It is corrosion and wear resistant. It is a Thule one-key system worth buying. ATTENTION PLEASE!!! If using this around salt water, spray silicone inside the locks. Safe & Secure When the lock cylinders on your racks are damaged or rusted, this is a security risk that will require you to replace them with new ones, thus deterring theft. Perfect if you have more than one Thule product. Install them in each one of your Thule racks, bars, cargo boxes, and more. That way, you only have to carry around one key. Makes things much easier. Easy to Install Install or replace the lock cylinders on your Thule products in a few easy steps. To replace an existing lock core, simply unlock it and use the included master key to remove it. Once the existing core has been removed, pop in the new One-Key System lock.