Twin size trundle , frame only, no mattress . Wheels smoothly under a twin or even a larger bed . Needs 12” of clearance height and 77” length. Never used still in box. I bought a white bed with matching trundle and they sent the wrong color trundle. This one is darker wood stain. I did get the white one eventually. It’s a great extra bed OR place a sheet of plywood over the slats and use it as a great storage or toy box