Abstract: A composition curable to a silicone elastomer is prepared by mixing a triorganosiloxy endblocked polydimethylsiloxane fluid where the triorganosiloxy is dimethylvinylsiloxy or methylphenylvinylsiloxy, a reinforcing silica having a surface treated with organosiloxane groups which contain 0.05 to 0.32 percent by weight vinyl, a hydroxy end-terminated polydiethylsiloxane fluid, an organohydrogensiloxane fluid, a platinum catalyst, and optionally a platinum catalyst inhibitor. The triorganosiloxy endblocked polydimethylsiloxane fluid has a major peak molecular weight of 68,000 to 135,000, a dispersity index greater than 3.8, the lowest molecular weight species between 854 and 3146 and the highest molecular weight species between 174,000 and 370,000. These compositions are readily extrudable under low pressure, have improved pot-life, cure to high strength elastomers with a high durometer, and have improved mold release.