About Sizes. - Wide range of sizes: The Frog Foot inner diameter starts from 13mm, 14mm, 15mm, 16mm, 17mm, 18mm,19mm,20mm And 21mm; If not sure about the sizes, may check the video before choose. How To Install. - Pull out the original chair foot (the black plastic pieces), they may or may not gule on the chair's metal tube. Replace the original feet with the Anti-Sink Frog Feet. Design Features. - Anti-Sink feature for sand, beach, mud, grass, gravel, rock, and etc. Made of thickend plastic, and rubber; Durable and sturdy; Design for different outdoor activities, such as fishing, camping, hiking, traveling, picnics, and etc; May store them in the mesh sport bag, which comes with the Frog Foot. Caution. - Do not use these Anti-Sink Forg Foot on slipery surfaces, such as tile, wood floor, slippy cement floor, or any slippy slope. The chassis is made of nylon material TAGUTA Furniture Cups Anti Sinking Frog Foot 4Pcs Chair Feet for Helinox/Naturehike/Moon LENCE/MARCHWAY Replacement Feet Furniture Foot Caps