The durability of coolant system hoses has improved in the recent past and various constructions are available to fit the different applications. Where the various constructions fit best is summarized below: 1. Rayon reinforced EPDM for normal use and durability. Handles almost all lower radiator hose applications. 2. Kevlar reinforced EPDM for places where heat is a problem to 150°C. Is not good in high flexing applications or as a by-pass hose. Fairly expensive. 3. Nomex reinforced EPDM has both heat and flex resistance. The only place this construction will not work is where there is an external source of heat, such as an exhaust manifold. Expensive. 4. Nomex reinforced Silicone is needed where extreme external heat is a problem. Very expensive.