Establishes a system of designation for poly(methyl methacrylate) thermoplastic materials which may be used as the basis for specifications. Applies to all poly(methyl methacrylate) (PMMA) homopolymers and copolymers of methyl methacrylate (MMA) containing at least 80% (m/m) of MMA and not more than 20% (m/m) of acrylic esters or other monomers. Does not apply to PMMA modified with elastomers.