Articles, in particular non-pressure mono- or multi-layer pipes, prepared by extrusion, molding and combination thereof, comprising a heterophasic polyolefin composition comprising (1) 65-95% of a crystalline propylene polymer insoluble in xylene at ambient temperature in an amount over 85% and having a polydispersity index ranging from 4 to 13 and an intrinsic viscosity value ([.eta.].sub.1) of over 2.2 dl/g, and (2) 5-35% of an elastomeric olefin polymer of ethylene with a C.sub.3-C.sub.10 .alpha.-olefin having an ethylene content ranging from 15 to 85% and an intrinsic viscosity value ([.eta.].sub.2) of at least 1.4 g/ml. The [.eta.].sub.1/[.eta.].sub.2 ratio ranging from 0.45 to 1.6. The articles typically have modulus of elasticity in tension higher than 2000 MPa.The invention also relates to the said heterophasic polyolefin composition and an extrusion process for producing the said articles.