Martin 6HS Quadraflex Sleeve, Hytrel, Inch, 3.75" OD, 1.875" Length For use with Martin S and SC type flanges in the Quadra-Flex series flexible coupling assemblies (sold separately) Thermoplastic polyester elastomer for high torque and high temperature applications Two types: one piece (Type H) and two-piece held together with a metal retaining ring (Type HS) for applications where space limitations prevent the installation of a one piece sleeve Teeth help to distribute torsional load across the sleeve and flanges, reducing wear and extending service life