this is not canon mount. I'm going to find out what it is and I asked my professor at school. Here are pictures of the mount on the lens that was sent to me. I will return it if I or a friend can't use it. I will return it if I can't use it. Oh I tried attaching it to a Canon AE1 film camera and it didn't work on that camera. I don't think it's a lens for a Canon camera. It drives me crazy to advertise it as such. This lens was for the Pentax K-mount. Check the bottom before you buy. and google the Pentax K-Mounts. Hope that helps. Note: I wish they had a photo from below. That's how I can tell if it's a Canon lens. best for you