The hama lens rear cap for canon eos is a must for any photographer using a slr or dslr camera this little piece of plastic is engineered to simply be positioned onto the mount at the rear of a lens when it has been removed and twisted to lock it into placerrit itakes just a second or two to position this and saves a lot of time and effort in cleaning the rear element a fiddly and precise task this rear lens cap also helps to protect the lens mount itself and the essential electronic contac