Stamina aero pilates is a very hard company to support. If something breaks on your machine and they have decided they no longer support your machine u are out of luck. Unlike other web sites where manuals and replacement parts aredisplayed for the consumer to select, stamina feels they must protect us from ourselves and if you cannot answer your model serial number and purchase date/place. They will not sell you the part you need. I own three machines and they refused to sell me a part because they could not be assured I wouldn't use it on one of my other machines. They said I could hurt myself with the round bit of foam I wanted to purchase. If you are buying a reformer from stamina... I get it they are cheap... Keep all this info handy. Most parts like these wheels are not available to the general public.