Mishimoto is proud to release a 3.0" to 3.5" transition silicone boot with DuraCore technology. Mishimoto DuraCore technology is the synthetic material that comprises the innermost layer of all Mishimoto silicone boots. Compared to normal silicone, DuraCore provides superior resistance to heat, pressure, fuel, and oil. This effectively increases the life of our boots by preventing leaks and blowouts.