(Pack of 10) 1-5/8" to 1-11/16" Round Black Vinyl Flexible End Cap Bolt Screw Rubber Thread Protector Safety Cover | for 1.625 Inch Pipe Post Tubing Rod OD Cover - 1" Inside Height.   This cap fits 1-5/8" OD (out side diameter of the tube/pipe) of the tube. Please do not try on bigger dia tubes. These are made of high quality PVC Vinyl by Caplugs, the World Leader in Plastics Molding and ISO 9001 certified.