A propylene polymer composition having a melt flow rate (MFR) value from 3 to 30 g/10 min, comprising (percent by weight): A) 50-90% of one or more propylene copolymer(s) having a content of xylene-insoluble mojety at room temperature of not less than 85%, selected from the group consisting of propylene-ethylene random copolymers containing from 1 to 7%, of ethylene; propylene-C4-C8 null-olefin copolymers containing 2-10% of the C4-C8 alpha-olefins; and propylene-ethylene-C4-C8 a-olefin copolymers containing 0.5-5% of ethylene and 2-6% Of C4-C8 null-olefins; and B) 10-50% of a copolymer of propylene containing from 8 to 40% of ethylene and optionally 1-10% of a C4-C8 alpha-olefin; the said MFR value (MFR (2)) being obtained by subjecting to degradation a precursor composition comprising the same components A) and B) in the above said proportions, but having the MFR value (MER (1)) from 0.1 to 5 g/10 min with a ratio MFR (2) to MFR (1) of from 1.5 to 20.