Originally posted by Racer X 69 What diameter is the cross section of the rubber?
Try 58 or 59 mm instead of 60. Its OK to stretch them out a tiny bit.
Also, get the orange silicone o-rings. The material is slippery so it will slide easier while mounting and unmounting lenses, and it is more durable than ordinary rubber.
The outside diameter (o/d) of the lens body just in front of the metal mount is 66mm (measured with a digital micrometer) and the internal diameter of the rings I have is (as stated in the previously-linked listing!!) 60mm (the o/d is 66mm) and they fit very snugly against the body. Rings smaller than that would be a pain to fit.
Wouldn't want to use silicone rubber because that is more "slippery" and so would be harder to fit to the lens and would fly off "somewhere" much more easily when the lens is removed from the body,
Anyway, this is a sort of experiment to see if the idea works, and I won't know that until I start shooting in the rain - but don't do that very often