HealthyExercize.com MacGregor Mac Collegiate Strapless -Single Base The base is made from rugged bonded polyester padding that is tear-resistant and waterproof. The base is easily bolted to its anchor plate. Anchor plate contains a metal sleeve for added stability. This base is designed to reduce sliding injuries, it is not a substitute for using proper sliding. 15" x 15" x 3" - Single base only.