This is a dedicated lens filter for lenses like the ALPA Kern-macro-switar. While standard lens filters are screw-in type, the macro-switar uses a push-in type. Kern-macro-switar lenses have recently become quite expensive, so why not protect your valuable lens glass? I used to attach this to my macro-switar 50mm f1.8. These are not commonly available, so don't miss out! Thank you for looking!