Single Size Test Ball is a must for those involved in the installation and repair of residential, commercial and industrial pipping systems. Can be used for head pressure testing or as a blocking plug for low-pressue air testing. Easily fits test tees, sanitary tees, floor drains and roof vents. Much more flexible than traditional mechanical plugs. Made from long-lasting, natural rubber. Molded with Cherne’s trademarked rib design. Includes a 12 In. removable zinc-plated steel chain for ease of replacement. Over-sized ring prevents the plug from being drawn into the pipe during testing. Withstands 13 psi air pressure or 30 Ft. of head pressure. 1/4 In. Schrader tire valve standard on all plugs.