This ring has been designed around the Canon CN-E 14 mm T3.1 wide-angle prime lens. The clamp-on ring allows the Lightweight Matte Boxes LMB-4A and LMB-6 to cover up to the full frame 24x36 mm sensor size (FF35) of EF mounted cameras such as Canon 1DC, 1D and 5D MkIII. The Canon lens is fitted with a front locating pin, which is compatible with the 156-114 mm ring.