Moulding compositions containingA. 6 to 30 parts by weight of graft polymer obtained by grafting 20 to 60 parts by weight of a mixture of styrene and acrylonitrile in a ratio by weight of 95 : 5 to 60 : 40 onto 80 to 40 parts by weight of polybutadiene or a butadiene copolymer with a butadiene content of at least 30% with an average particle diameter of 0.26 to 0.65.mu. and a grafting degree of 0.15 to 0.7;B. 14 to 45 parts by weight of a graft polymer obtained by polymerizing 40 to 60 parts by weight of a mixture of styrene and acrylonitrile in a ratio by weight of 95 : 5 to 60 : 40 onto 60 to 40 parts by weight of polybutadiene or a butadiene copolymer with a butadiene content of at least 30%, with an average particle diameter of 0.05 to 0.25.mu. and a grafting degree of 0.4 to 0.9; andC. 25 to 80 parts by weight of a copolymer of styrene and/or .alpha.-methyl styrene on the one hand and acrylonitrile on the other hand in a ratio by weight of 80 : 20 to 60 : 40 and an average molecular weight (mean weight) M.sub.w of 50,000 to 200,000 and a molecular heterogeneity of U = 4.5 to 1.0.