I really prefer rubber bellows cloth for rotary pumps, because it is
what was used originally.  However, after using many inferior grades
of rubber cloth that failed in a short period of time, I gave up and
tried kangaroo hide which has not stretched or presented any problems
in 29 years!

If I could obtain a reliable rubber bellows cloth today, I would use
it, but there is no test other than time itself.

After 45 years of player work, it is getting very difficult for me to
get down on the floor and pull a pump from a piano, and once I do it,
I do not want to do it over in a short time.

Bruce Clark