A polyolefin composition comprising: A) from 30% to 90% by weight of a propylene polymer composition comprising: a1) from 20% to 90% by weight of a propylene homopolymer or of a copolymer of propylene or blends thereof, containing 8% by weight or less of copolymerized ethylene or C 4 -C 10 α-olefin(s) or blends thereof, said homopolymer or copolymer or blends having an isotactic index higher than 80%; a2) from 10% to 80% by weight of a copolymer of ethylene containing from 40% to 70% by weight of copolymerized propylene or C 4 -C 10 α-olefin(s) or of combinations thereof; said composition A having intrinsic viscosity of the xylene soluble fraction at room temperature of from 1.5 to 8 dl/g; (ASTM D 2857) B) from 10% to 70% by weight of a multimodal ethylene copolymer with butene-1 as comonomer having the following properties: i) density comprised in the range from 0.850 to 0.935 g/cm 3 as measured according to ISO1183-1::2004; ii) total butene-1 comonomer content ranging from 6% to 30% by weight; iii) Mw/Mn comprised from 4 to 20; iv) intrinsic viscosity, as determined in decalin at 135°C according to EN ISO 1628-312003, comprised between 1.0 and 4.0 dL/g, and comprising an HDPE fraction (HDPE %wt) determined via TREF analysis of up to 30%wt C) up to 50 % by weight of a filler. A) from 30% to 90% by weight of a propylene polymer composition comprising: a1) from 20% to 90% by weight of a propylene homopolymer or of a copolymer of propylene or blends thereof, containing 8% by weight or less of copolymerized ethylene or C 4 -C 10 α-olefin(s) or blends thereof, said homopolymer or copolymer or blends having an isotactic index higher than 80%; a2) from 10% to 80% by weight of a copolymer of ethylene containing from 40% to 70% by weight of copolymerized propylene or C 4 -C 10 α-olefin(s) or of combinations thereof; said composition A having intrinsic viscosity of the xylene soluble fraction at room temperature of from 1.5 to 8 dl/g; (ASTM D 2857) a1) from 20% to 90% by weight of a propylene homopolymer or of a copolymer of propylene or blends thereof, containing 8% by weight or less of copolymerized ethylene or C 4 -C 10 α-olefin(s) or blends thereof, said homopolymer or copolymer or blends having an isotactic index higher than 80%; a2) from 10% to 80% by weight of a copolymer of ethylene containing from 40% to 70% by weight of copolymerized propylene or C 4 -C 10 α-olefin(s) or of combinations thereof; said composition A having intrinsic viscosity of the xylene soluble fraction at room temperature of from 1.5 to 8 dl/g; (ASTM D 2857) B) from 10% to 70% by weight of a multimodal ethylene copolymer with butene-1 as comonomer having the following properties: i) density comprised in the range from 0.850 to 0.935 g/cm 3 as measured according to ISO1183-1::2004; ii) total butene-1 comonomer content ranging from 6% to 30% by weight; iii) Mw/Mn comprised from 4 to 20; iv) intrinsic viscosity, as determined in decalin at 135°C according to EN ISO 1628-312003, comprised between 1.0 and 4.0 dL/g, and comprising an HDPE fraction (HDPE %wt) determined via TREF analysis of up to 30%wt i) density comprised in the range from 0.850 to 0.935 g/cm 3 as measured according to ISO1183-1::2004; ii) total butene-1 comonomer content ranging from 6% to 30% by weight; iii) Mw/Mn comprised from 4 to 20; iv) intrinsic viscosity, as determined in decalin at 135°C according to EN ISO 1628-312003, comprised between 1.0 and 4.0 dL/g, C) up to 50 % by weight of a filler.