Curable organosiloxane compositions

The tear strength of cured organosiloxane elastomers can be increased without adversely affecting other physical properties if the composition used to prepare the elastomer is curable by a platinum-catalyzed hydrosilation reaction and contains a mixture of two liquid diorganovinylsiloxy terminated polydiorganosiloxanes, one of which constitutes from 70 to 95 percent by weight of said mixture and contains vinyl or other ethylenically unsaturated hydrocarbon radicals only at the terminal positions. The second polydiorgansiloxane contains both terminal vinyl radicals and from 1 to 5 mole percent of vinyl radicals on non-terminal repeating units. .