The CRC-1 Lens Collar from Kirk is a replacement lens collar for the Canon EF 180mm f/3.5L Macro USM, EF 300mm f/4L IS USM, EF 70-200mm f/2.8L IS II USM, EF 70-200mm f/2.8L IS III USM, 100mm f/2.8 Macro, EF 100-400mm f/4.5-5.6L IS II USM, MP-E 65mm f/2.8 1-5x Macro lenses. It is designed to increase stability when using the lens on a tripod or monopod. The collar features an integrated Arca-style base plate for mounting to any compatible quick-release clamp.