Designed for use on concrete, gravel, and other hard surfaces, the 3 Legged Thing Heelz Tripod Leg Spikes are made of strong and durable milled stainless steel for longevity and stability. You get a set of three spikes—one for each tripod leg—and each is outfitted with a dual 1/4"-20 and 3/8"-16 threaded mounting stud to be compatible with a wide assortment of tripods.