The invention relates to a pellet comprising a thermoplastic polymer sheath intimately surrounding glass filaments, which glass filaments are covered at least in part with an impregnating agent and extend in a longitudinal direction of said pellets, wherein the thermoplastic polymer sheath is prepared from a thermoplastic polymer composition comprising A) a heterophasic propylene copolymer consisting of a propylene-based matrix and a dispersed ethylene-α-olefin copolymer, wherein the heterophasic propylene copolymer has a melt flow rate of at least 40 g/10 min as determined in accordance with ISO 1133 (230° C., 2.16 kg) and a FOG value of at most 350 μg/g as determined by VDA 278, wherein the glass filaments are present in an amount of 10-70 wt % based on the pellet.