Actually I thought about using Plywood but...Unless you used the Really Good expensive stuff with Multiple Plies it would not be as good as the MDF. MDF is very stable and Unless it gets wet Is perfect for this application. I did seal it with Sanding Sealer but I didn't want it to Slick so the belt would have some BITE. My machine is a Vintage REX 11-155R I had problems getting her to sew properly at first. Finally discovered the hook had a miniscule burr on it . Once I got that sanded out and polished she's sewing like a brand new machine. I've since made another wheel for a friend and painted it Gloss Black. He didn't Like it due to the fact that it didn't slide on his hand as well. Told him to wax it. Not sure if he ever did. I meant a NERF Ball not a Smurf Ball!!!! :)