Poly Urethane (PU) - Models with suffix U
Polyurethane is unbelievably tough and is the strongest and best boat material available. It is weldable for construction - which means there is no glue to deteriorate - and yet is easily repairable with glue. PU has better properties than any other inflatable boat material in all categories except foldability (Hypalon is easier to fold). We have had 15 year old PU commercial rafts come in with fittings for repair (ropes, d-rings, early era glue lines) but with the basic boat material looking like new.
 

Polyurethane Alloy - Whitewater models with suffix X, Sally, sea-kayaks, and Waterstrider
Polyurethane can be alloyed with PVC, and Incept offers options for the larger rafts of 100% PU throughout, or a 50/50 blend in the sponsons and 100% PU in the floors, gaining a significant saving in cost and retaining many of the advantages of polyurethane's toughness. Smaller boats with suffix-X use the PU blend throughout.