Abstract: Compositions based on propylene polymers (compositions (C)) comprising: a) from 61 to 74% by weight of a random propylene copolymer (copolymer (A)) comprising from 8 to 16% by weight of monomer units derived from 1-butene and less than 0.5% by weight of monomer units derived from ethylene, and b) from 39 to 26% by weight of a random propylene copolymer (copolymer (B)) comprising from 35 to 50% by weight of monomer units derived from 1-butene and from 0 to 1% by weight of monomer units derived from ethylene. Process for the manufacture of these compositions.