The invention relates to a composition comprising (a) polypropylene having a melt mass flow rate as measured in accordance with ISO 1133 using a 2.16 kg weight and at a temperature of 230° C. in the range from 10 to 40 g/10 min and (b) a polymer preferably chosen from the group consisting of polyoxymethylene, polyamide and mixture thereof, wherein the amount of component (b) is from 0.005 to 5 wt % based on the total weight of the components (a) and (b) and wherein the polypropylene has a melt temperature TmPP and a crystallization temperature TcPP, the polymer has a melt temperature TmP and a crystallization temperature TcP, wherein the TcP is 5-40° C. higher than TcPP, wherein the Tm and Tc are determined using Differential Scanning Calorimetry according to ASTM D 3418-08 using a scan rate of 10° C./min on a sample of 10 mg and using the second heating cycle.