These are a set of 3 Industrial Caster Wheels. 2 of them are swivel and one is not, they also will need to have nuts added to the bolts. The wheels are pre-owned and used, but looks to be in good working order. The diameter of the wheels are 4". The plates are made of a cast steel material and the wheels are either a very hard rubber or plastic material. Wheels like this are expensive new. I have a few more listed if interested take a look. Good Luck.