An improvement in isostatic pressure molding wherein a flexible container having a fluid-like medium is realized by using as the medium a silicone crumb in a fine particulate form having an extrusion rate of at least 50 grams per minute through an orifice of 0.5 inch diameter under a pressure of 345 kilopascals and compression points of less than 1035 kilopascals. This crumb is made from a vinyl-containing polyorganosiloxane, a silicon-bonded hydrogen containing polysiloxane, and a platinum catalyst.