Polyurethane coupling inserts also called PU spiders or urethane coupling spiders are made from excellent quality PU produced by companies and with many designs,colors and sizes available for buyer’s option including series of GR,GS,MT,T,L,R,NM,MH,HRC,YOX etc.And also can be customized according to buyers' special requirements.They are the key parts to jaw type flexible couplings.