In {TAIL ~ faster RIM type systems}, {HEAD ~ the faster MDI} would normally be the diisocyanate of choice 
In { TAIL ~ faster RIM type systems } , { HEAD ~ the faster MDI } would normally be the diisocyanate of choice
REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH