A thermoplastic moulding composition, comprising, as components to, A) from 10 to 70% by weight of a graft polymer having a bimodal particle size distribution, made, based on, a 1) from 40 to 90% by weight of an elastomeric particulate graft base (a 1), obtained by emulsion polymerization of, based on (a 1), a 11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C 1-8 -alkyl acrylate, or of mixtures of these, a 12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a 13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer. a 2) from 10 to 60% by weight of a graft a 2), made, based on a 2), a 21) from 65 to 95% by weight of at least one vinyl aromatic monomer, a 22) from 5 to 35% by weight of acrylonitrile, a 23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a 24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer having a viscosity number VN of from 50 to 120 ml/g, made, based on, b 1) from 74 to 78% by weight of at least one vinyl aromatic monomer, b 2) from 22 to 26% by weight of acrylonitrile, and b 3) from 0 to 4 % by weight of at least one other monoethylenically unsaturated monomer; C) from 1.2 to 3% by weight of a thermoplastic polymer having a viscosity number VN of from 50 to 120 ml/g, made, based on, c 1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c 2) from 17 to 35% by weight of acrylonitrile and c 3) from 1 to 10 % by weight of at least one other monoethylenically unsaturated monomer, where the vinyl aromatic content of component is at least 2 units but not more then 4.9 units (% by weight), lower compared to that of component; D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E. A) from 10 to 70% by weight of a graft polymer having a bimodal particle size distribution, made, based on, a 1) from 40 to 90% by weight of an elastomeric particulate graft base (a 1), obtained by emulsion polymerization of, based on (a 1), a 11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C 1-8 -alkyl acrylate, or of mixtures of these, a 12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a 13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer. a 2) from 10 to 60% by weight of a graft a 2), made, based on a 2), a 21) from 65 to 95% by weight of at least one vinyl aromatic monomer, a 22) from 5 to 35% by weight of acrylonitrile, a 23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a 24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; a 1) from 40 to 90% by weight of an elastomeric particulate graft base (a 1), obtained by emulsion polymerization of, based on (a 1), a 11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C 1-8 -alkyl acrylate, or of mixtures of these, a 12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a 13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer. a 11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C 1-8 -alkyl acrylate, or of mixtures of these, a 12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a 13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer. a 2) from 10 to 60% by weight of a graft a 2), made, based on a 2), a 21) from 65 to 95% by weight of at least one vinyl aromatic monomer, a 22) from 5 to 35% by weight of acrylonitrile, a 23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a 24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; a 21) from 65 to 95% by weight of at least one vinyl aromatic monomer, a 22) from 5 to 35% by weight of acrylonitrile, a 23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a 24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer having a viscosity number VN of from 50 to 120 ml/g, made, based on, b 1) from 74 to 78% by weight of at least one vinyl aromatic monomer, b 2) from 22 to 26% by weight of acrylonitrile, and b 3) from 0 to 4 % by weight of at least one other monoethylenically unsaturated monomer; b 1) from 74 to 78% by weight of at least one vinyl aromatic monomer, b 2) from 22 to 26% by weight of acrylonitrile, and b 3) from 0 to 4 % by weight of at least one other monoethylenically unsaturated monomer; C) from 1.2 to 3% by weight of a thermoplastic polymer having a viscosity number VN of from 50 to 120 ml/g, made, based on, c 1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c 2) from 17 to 35% by weight of acrylonitrile and c 3) from 1 to 10 % by weight of at least one other monoethylenically unsaturated monomer, where the vinyl aromatic content of component is at least 2 units but not more then 4.9 units (% by weight), lower compared to that of component; c 1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c 2) from 17 to 35% by weight of acrylonitrile and c 3) from 1 to 10 % by weight of at least one other monoethylenically unsaturated monomer, D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E.