A poly(methyl methacrylate) resin composition comprising: (a) 30 to 90 weight % of a methyl methacrylate polymer, based on the total weight of the poly(methyl methacrylate) resin composition, comprising polymerized structural units of (i) 50 to 100 weight % methyl methacrylate monomer, based on the total weight of the methyl methacrylate polymer, and (ii) 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the methyl methacrylate polymer; (b) 10 to 70 weight % of a multistage acrylic impact modifier, based on the total weight of the poly(methyl methacrylate) resin, comprising (i) 50 to 99 weight % of a core-shell polymer, based on the total weight of the multistage acrylic impact modifier, comprising 50 to 99.9 weight % of a core polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 98.2 to 99.8 weight % of C 1 -C 12 alkyl acrylate monomers, and 0.2 to 1.8 weight % of a cross-linker, based on the total weight of the core polymer, and 0.1 to 50 weight % of a shell polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 50 to 100 weight % methyl methacrylate monomers, and 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the shell polymer, and (ii) 1 to 50 weight % of an overpolymer, based on the total weight of the multistage acrylic impact modifier, comprising polymerized structural units of 50 to 99.95 weight % methyl methacrylate monomers, based on the total weight of the overpolymer, 0.05 to 2 weight % of a chain transfer agent, based on the total weight of the overpolymer, and 0 to 49.95 weight % of a copolymerizable monomer. (a) 30 to 90 weight % of a methyl methacrylate polymer, based on the total weight of the poly(methyl methacrylate) resin composition, comprising polymerized structural units of (i) 50 to 100 weight % methyl methacrylate monomer, based on the total weight of the methyl methacrylate polymer, and (ii) 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the methyl methacrylate polymer; (i) 50 to 100 weight % methyl methacrylate monomer, based on the total weight of the methyl methacrylate polymer, and (ii) 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the methyl methacrylate polymer; (b) 10 to 70 weight % of a multistage acrylic impact modifier, based on the total weight of the poly(methyl methacrylate) resin, comprising (i) 50 to 99 weight % of a core-shell polymer, based on the total weight of the multistage acrylic impact modifier, comprising 50 to 99.9 weight % of a core polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 98.2 to 99.8 weight % of C 1 -C 12 alkyl acrylate monomers, and 0.2 to 1.8 weight % of a cross-linker, based on the total weight of the core polymer, and 0.1 to 50 weight % of a shell polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 50 to 100 weight % methyl methacrylate monomers, and 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the shell polymer, and (ii) 1 to 50 weight % of an overpolymer, based on the total weight of the multistage acrylic impact modifier, comprising polymerized structural units of 50 to 99.95 weight % methyl methacrylate monomers, based on the total weight of the overpolymer, 0.05 to 2 weight % of a chain transfer agent, based on the total weight of the overpolymer, and 0 to 49.95 weight % of a copolymerizable monomer. (i) 50 to 99 weight % of a core-shell polymer, based on the total weight of the multistage acrylic impact modifier, comprising 50 to 99.9 weight % of a core polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 98.2 to 99.8 weight % of C 1 -C 12 alkyl acrylate monomers, and 0.2 to 1.8 weight % of a cross-linker, based on the total weight of the core polymer, and 0.1 to 50 weight % of a shell polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 50 to 100 weight % methyl methacrylate monomers, and 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the shell polymer, and 50 to 99.9 weight % of a core polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 98.2 to 99.8 weight % of C 1 -C 12 alkyl acrylate monomers, and 0.2 to 1.8 weight % of a cross-linker, based on the total weight of the core polymer, and 0.1 to 50 weight % of a shell polymer, based on the total weight of the core-shell polymer, comprising polymerized structural units of 50 to 100 weight % methyl methacrylate monomers, and 0 to 50 weight % of a copolymerizable monomer, based on the total weight of the shell polymer, and (ii) 1 to 50 weight % of an overpolymer, based on the total weight of the multistage acrylic impact modifier, comprising polymerized structural units of 50 to 99.95 weight % methyl methacrylate monomers, based on the total weight of the overpolymer, 0.05 to 2 weight % of a chain transfer agent, based on the total weight of the overpolymer, and 0 to 49.95 weight % of a copolymerizable monomer. 50 to 99.95 weight % methyl methacrylate monomers, based on the total weight of the overpolymer, 0.05 to 2 weight % of a chain transfer agent, based on the total weight of the overpolymer, and 0 to 49.95 weight % of a copolymerizable monomer.