Working with Vibram, Helinox developed these round rubber feet to help secure your chair on hard ground and slippery surfaces. The Vibram rubber compound is sticky, durable, and won’t mark backcountry granite or your home’s wood floors, and the round shape adds a little more surface area to help offset sinking into softer ground. The 45mm size works with Helinox’s Chair Ones, Chair Two, and Chair Zero.