Tamron stands apart from other lens manufacturers with its use of an interchangeable mount system instead of a fixed-mount. Fixed-mount lenses are limited to use on cameras using that specific mount system. The Tamron interchangeable mount system makes Tamron's manual focus lenses compatible with a wide range of SLR cameras so you can change your camera without having to change your lens. In fact, Tamron offers approximately 20 different mounts usable with some 200 35mm SLRs.