Quoted from silver_spinner:i got a set of those rubbers as mine were missing as well and the inside circumference is way way smaller than the posts they go on. these things are as hard as hockey pucks and wont stretch either. did steve send the wrong ones or is there a magic way to put them on. i gave him the correct part number.
Another option is to use old brown rebound rubbers. I did this years ago, and it worked great. A buddy has the machine now. I'll have to ask him if the rubbers are holding up.