I have a very good NAPA climbing plant that I have used for many years. It has five wheels and one started to fail. I found a set of impellers with roughly the same diameter (3 inches) and the same thread on the spindle (M10x1.5). This set had the narrowest diameter wheel I could find with the same thread pitch on the spindle. Luckily I settled on a set of wheels with the same spindle size as this set of six wheels only came with four nuts. Although it seems to work fine on my good old Creeper.