We purchased a VigorFit® machine so we could take measurements of the wheel assemblies and rails so that we could optimize our design and then evaluate our upgraded wheel. We were able to increase the rolling diameter and thicken the flange portion of the wheel to strengthen the wheel. We machine the wheel from much stronger solid engineering plastic like our other wheels. The wheel fits nicely on the rails and is much stronger than the original wheels. As many have reported to us, one of our original wheels was broken when we received it. A large portion of the flange was broken off of one of our wheels. We have made an installation instructional video instead of written instructions for this wheel since the installation is more complicated than for a Total Gym. These wheels should last an extremely long time and hopefully forever.