Round dolly simplifies moving around empty or full trash receptacles (sold separately). Simply set your empty receptacle on the dolly and lock it into place with a quick quarter turn. Full or empty, the receptacle rolls easily where you need it on the five nonmarking, 3″ gray casters. Dolly is designed to fit round Genuine Joe trash receptacles that hold 32, 44 or 55 gallons. The 17.91″ diameter dolly is made of heavy-duty engineered resins. Upper diameter on the raised block that inserts into receptacle bottom measures 10.63″.