Typically used on base of swivel chairs. The stem bumpers keep the round base of the patio chair from sitting directly on the ground. Most swivel bases use 6 to 8 stem bumpers per chair. Stem bumpers can be flat or coved (curved) to fit the shape of the tubular metal of the patio chair base. This coved stem bumper fits 1/4" hole and is about 1/2" long (the stem can be cut to fit length as needed). The base disc is 3/4" round and is coved to fit over round tubing.