A polyethylene composition comprising: A) from 65% to 97% by weight of a copolymer of ethylene with one or more comonomers selected from C 3 -C 10 alpha-olefins, said ethylene copolymer having the following features: 1) a density of 0.925 g/cm 3 or higher, measured according to ISO 1183-1:2012 at 23°C; 2) a MI 2 value of 0.5 g/10 min. or greater, where MI 2 is the Melt Index measured according to ISO 1133-2:2011 at 190°C with a load of 2.16 kg; B) from 3% to 35% by weight of a polyolefin composition comprising: B I) from 5% to 35% by weight of a propylene homopolymer containing 10.0% by weight or less of a fraction soluble in xylene at 25°C (XS I), referred to the weight of B I); B II) from 20% to 50% by weight of an ethylene homopolymer or a copolymer ethylene with up to 5% by weight of one or more comonomers selected from C 3 -C 10 alpha-olefins, both homopolymer and copolymer containing 5% by weight or less of a fraction soluble in xylene at 25°C (XS II), both the amount of comonomers and the amount of the fraction XS II being referred to the weight of B II); and B III) from 30% to 60% by weight of a terpolymer of ethylene, propylene and butene-1 containing from 45% to 65% by weight of ethylene units, and from 15% to 38% by weight-of 1-butene units, and containing from 30% to 85% by weight of a fraction soluble in xylene at 25°C (XS III), the amounts of ethylene units and butene-1 units and of the fraction XS III being all referred to the weight of B III); the said amounts of A) and B) being referred to the total weight of A) + B) and the said amounts of B I), B II) and B III) being referred to the total weight of B I) + B II) + B III). A) from 65% to 97% by weight of a copolymer of ethylene with one or more comonomers selected from C 3 -C 10 alpha-olefins, said ethylene copolymer having the following features: 1) a density of 0.925 g/cm 3 or higher, measured according to ISO 1183-1:2012 at 23°C; 2) a MI 2 value of 0.5 g/10 min. or greater, where MI 2 is the Melt Index measured according to ISO 1133-2:2011 at 190°C with a load of 2.16 kg; 1) a density of 0.925 g/cm 3 or higher, measured according to ISO 1183-1:2012 at 23°C; 2) a MI 2 value of 0.5 g/10 min. or greater, where MI 2 is the Melt Index measured according to ISO 1133-2:2011 at 190°C with a load of 2.16 kg; B) from 3% to 35% by weight of a polyolefin composition comprising: B I) from 5% to 35% by weight of a propylene homopolymer containing 10.0% by weight or less of a fraction soluble in xylene at 25°C (XS I), referred to the weight of B I); B II) from 20% to 50% by weight of an ethylene homopolymer or a copolymer ethylene with up to 5% by weight of one or more comonomers selected from C 3 -C 10 alpha-olefins, both homopolymer and copolymer containing 5% by weight or less of a fraction soluble in xylene at 25°C (XS II), both the amount of comonomers and the amount of the fraction XS II being referred to the weight of B II); and B III) from 30% to 60% by weight of a terpolymer of ethylene, propylene and butene-1 containing from 45% to 65% by weight of ethylene units, and from 15% to 38% by weight-of 1-butene units, and containing from 30% to 85% by weight of a fraction soluble in xylene at 25°C (XS III), the amounts of ethylene units and butene-1 units and of the fraction XS III being all referred to the weight of B III); B I) from 5% to 35% by weight of a propylene homopolymer containing 10.0% by weight or less of a fraction soluble in xylene at 25°C (XS I), referred to the weight of B I); B II) from 20% to 50% by weight of an ethylene homopolymer or a copolymer ethylene with up to 5% by weight of one or more comonomers selected from C 3 -C 10 alpha-olefins, both homopolymer and copolymer containing 5% by weight or less of a fraction soluble in xylene at 25°C (XS II), both the amount of comonomers and the amount of the fraction XS II being referred to the weight of B II); and B III) from 30% to 60% by weight of a terpolymer of ethylene, propylene and butene-1 containing from 45% to 65% by weight of ethylene units, and from 15% to 38% by weight-of 1-butene units, and containing from 30% to 85% by weight of a fraction soluble in xylene at 25°C (XS III), the amounts of ethylene units and butene-1 units and of the fraction XS III being all referred to the weight of B III);