Stem bumpers are typically used on the bottom of round swivel base patio chairs. The stem bumpers keep the round base of the patio chair from siting directly on the ground. Most swivel base patio chairs 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. Chair Care Patio Furniture Repair has a large selection of patio furniture repair parts to fit a variety of outdoor patio furniture styles. Round patio chair glides and stem bumpers are sized to fit common patio furniture chair. You can find more information about how to measure for patio furniture replacement parts in the FAQ section of our website.