NEW and improved design!! Rubber End Cap for IV Stabolution is made out to Neoprene Rubber which is a blend of SBR (Styrene Butadiene Rubber), CR (Neoprene) and NBR (Nitrile) rubbers. It is a high quality rubber which is light weight, absorbs shock and resistant to many chemicals and oil. This model can only be used on any length Stabolution IV models Diameter: 1/2" Compatible with Stabolution lengths: 6"-36" with a 1/2" Diameter