Glass fibers are used in RRIM Urethane to provide dimensional stability and good physical properties - particularly impact strength. However, 1/16″ milled glass fibers have the disadvantages of high cost (approximately 82c/lb., anisotropic impact properties and difficult handling and process characteristics. Acicular type fillers, such as Wollastonite, provide tempting substitution possibilities because of lower price, isotropic impact properties and inherent easier handling. However, untreated Wollastonite grades provided inferior properties when compared to silane sized 1/16″ milled fiberglass. Silane treated Wollastonite, G Wollastokup 1100 0.5, has shown promise but falls short in the important area of impact.This paper will demonstrate that the use of Wollastokup KR TTS 0.5 (22c/lb.) appears to provide equivalent impact while elongation, tear strength, tensile strength and flexural modulus are higher, process viscosity 16% lower and offering a 60c/lb. savings when compared to silane sized 1/16″ milled fiberglass at the 40% loading level (24.1% on total composite) in hydroxyl component.