Thermoplastic polymer composition (P) comprising: (A) up to 99.75 wt.-% of at least one styrene-based polymer composition (A) comprising at least one graft copolymer (A-1); (B) 0.25 to 5 wt.-% of at least one organopolysiloxane compound; (C) 0 to 10 wt.-% of at least one colorant, dye or pigment; and (D) 0 to 3 wt.-% of at least one further additive; wherein the constituents (A) to (D) sum up to 100 wt.-% of the thermoplastic polymer composition (P); and wherein • the styrene-based polymer composition (A) comprises 20 to 60 wt.-%, preferably 30 to 40 wt.-%, of at least one styrene-based graft copolymer (A-1) and 40 to 80 wt.-%, preferably 60 to 70 wt.-%, of at least one thermoplastic polymer (A-2) selected from poly(styrene-acrylonitrile) (SAN), poly(a-methyl styrene-acrylonitrile) (AMSAN) and mixtures thereof; • the at least one organopolysiloxane compound (B) has a weight average molecular weight Mw of 20,000 g/mol to 100,000 g/mol, determined by gel permeation chromatography (GPC) relative to polystyrene as standard and THF as solvent; • wherein the at least one organopolysiloxane compound (B) is a block copolymer comprising blocks of polysiloxane moieties comprising repeating units having the following formula (Ia): wherein each R 1 is independently selected from a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10, preferably 1 to 6, carbon atoms, and blocks of polyester and/or polyolefin moieties; and • the at least one graft copolymer (A-1) is selected from a poly(acrylonitrile-butadiene-styrene) (ABS) having an average particle size D 50 of the rubber particles in the ABS copolymer from 50 to 750 nm, a poly(acrylonitrile-styrene-acrylic ester) (ASA) having an average particle size D 50 of the rubber particles in the ASA copolymer from 50 to 1000 nm, and mixtures thereof, wherein the average particle size is determined using an ultracentrifuge. (A) up to 99.75 wt.-% of at least one styrene-based polymer composition (A) comprising at least one graft copolymer (A-1); (B) 0.25 to 5 wt.-% of at least one organopolysiloxane compound; (C) 0 to 10 wt.-% of at least one colorant, dye or pigment; and (D) 0 to 3 wt.-% of at least one further additive; • the styrene-based polymer composition (A) comprises 20 to 60 wt.-%, preferably 30 to 40 wt.-%, of at least one styrene-based graft copolymer (A-1) and 40 to 80 wt.-%, preferably 60 to 70 wt.-%, of at least one thermoplastic polymer (A-2) selected from poly(styrene-acrylonitrile) (SAN), poly(a-methyl styrene-acrylonitrile) (AMSAN) and mixtures thereof; • the at least one organopolysiloxane compound (B) has a weight average molecular weight Mw of 20,000 g/mol to 100,000 g/mol, determined by gel permeation chromatography (GPC) relative to polystyrene as standard and THF as solvent; • wherein the at least one organopolysiloxane compound (B) is a block copolymer comprising blocks of polysiloxane moieties comprising repeating units having the following formula (Ia): wherein each R 1 is independently selected from a linear or branched, saturated or unsaturated hydrocarbon group having 1 to 10, preferably 1 to 6, carbon atoms, and blocks of polyester and/or polyolefin moieties; and • the at least one graft copolymer (A-1) is selected from a poly(acrylonitrile-butadiene-styrene) (ABS) having an average particle size D 50 of the rubber particles in the ABS copolymer from 50 to 750 nm, a poly(acrylonitrile-styrene-acrylic ester) (ASA) having an average particle size D 50 of the rubber particles in the ASA copolymer from 50 to 1000 nm, and mixtures thereof, wherein the average particle size is determined using an ultracentrifuge. <EOS>