Polyurethane coupling inserts also called PU spiders or urethane coupling spiders are made of excellent qualityPU from famous companies and with varieties of designs,colors and sizes including series of GR,GS,MT,T,L,R,NM,MH,HRC,YOX etc.And also canbecustomized according to buyers' special requirements.They are the key parts to jaw type flexible couplings.