Four large plastic rings/discs with holes big enough to fit legs and hands. They seem to be adjustable to fit any size. If you look closely there’s strings attached to them that attach to the roof! They do something. Made by Luna Co. (Note: the rings/disc can auto-adjust.). It seems they were made to be put on for some reason. There is a fifth, bigger one for the torso nearby, sitting on the kitchen bench with a string also attached to it.