The tube is an oddball size so I had to cut the felts too big. I cut the first holes at .250, but when I squeezed the felt in it reduced the hole to much, so I had to go to a 3/8 punch, that made it just right. if I find some steel washers the right size I will try them. why couldn't I make the wipers out of a harder rubber of some kind, or teflon? or nylon? plexiglass? all should work and be lighter than steel. that this thing worked at all kinda impressed me, let alone worked well, for someone floundering around in the dark it's cool! Dave.