This report describes certification of the Mw of SRM 2888, a polystyrene (PS), by light scattering. As supplemental numbers, the Mn by NMR end group analysis and the Mw, Mn and the MMD by MALDI-TOF-MS are also given. SRM 2888 was prepared commercially for NIST Polymers Division for use as a standard for Size Exclusion Chromatography and as a narrow distribution polymer standard with well-defined classical molecular mass moments for comparative studies by MALDI-MS. This material was specially prepared and characterized for well-defined end groups. After packaging of this material for future distribution, the Mw was determined by light scattering and Mn determined by solution NMR. End groups were further studied by FTIR and MALDI-TOF-MS. The MMD was studied by MALDI-TOF-MS. The bottle-to-bottle homogeneity of this Standard Reference Material (SRM) was examined by size exclusion chromatography (SEC).