The Wheel Base Assembly includes the slide overlocking latches which lock the crate onto the wheel base. Four 6" foam filled no flat wheels, 2 of which include toe locks. Frame is powdercoated Black. Crate Wheel Base is available for all crates in single, stack, quad, six pack or any configuration you choose. Attaching clips are on the front and back of the wheel base. You will need a 3/4” socket wrench (not provided) to attach the casters securely to the base.