Geloy weatherable resin is composed of a modified terpolymer, which is formed by blending an amorphous thermoplastic copolymer of acrylonitrile (A) and styrene (S) with an elastomeric component. The latter is typically based on acrylate rubber (A) or possibly other elastomers. The difference between an ABS and an ASA is the use of the acrylic elastomer. Each of the three monomers offers different properties. The use of a three monomer system therefore allows the property profile of the Geloy resin to be tailored to meet a broad range of end-use requirements. The use of saturated rubber gives the Geloy resin family its long-term UV resistance, thereby enabling it to retain its high level of impact strength, gloss and color after prolonged exposure to many kinds of adverse environments. As a result, savings may be achieved through the elimination of costly painting of applications.