Kood Step-Down Ring 77mm - 72mm

So these have helped me to be able to use a Sunpak Ring-Flash on a number of lenses that I couldn't have used it on before - but, man, are they difficult to get off again!! They sit very tight, and, particularly if you screw them into a lens filter ring, pretty impossible to get off. I've tried on a couple and given up because I don't want to damage the lens filter!