This ZEISS Interchangeable Mount Set allows users to convert their 21 - 100mm T2.9-3.9 Light Weight Zoom LWZ.3 Lens to EF-Mount. The set includes the mount ring, color coded shims, and a rear lens cap. As the flange focal distance varies from camera type to camera type, it is sometimes necessary to make adjustments when changing the lens mount or camera model. In order to perform this adjustment shims are provided in multiple thicknesses.