A process and composition for MBS modifiers having (A) a rubbery core, (B) an inner graft stage comprised mainly of a hard polymer, (C) an intermediate sealer stage comprised mainly of an alkyl acrylate monomer and/or a polyunsaturated crosslinker, and (D) an outer shell to provide compatibility of the core-shell polymer with the matrix polymer, is disclosed. A process for preparing MBS impact modifiers having suprisingly improved impact performance in matrix polymers is also disclosed. Articles prepared from blends of matrix polymers and the MBS core-shell polymers described herein are also disclosed.