The invention provides a flexible plastic formulation capable of being extruded, blow-molded, ethylene oxide and radiation sterilized. The plastic formulation of the invention comprises: a) from about 60 to about 94 percent by weight of a copolymer consisting essentially of ethylene and vinyl acetate units; b) from about 5 to about 25 percent by weight of a block copolymer, the block copolymer consisting essentially of a central block copolymer molecule including generally equal proportions of ethylene and butylene units, and terminal blocks of polystyrene; and c) from about 1 to about 15 percent by weight of an ultra-low density polyethylene material. The plastic formulations of the invention are useful in the manufacture of blood bags, tubing and the like.