Abstract: Thermally curate resin composition, having shrink-controlled properties and being suitable for use in sheet moulding compounds and bulk moulding compounds (SMCs and BMCs) comprising, inter alia (a) an unsaturated polyester; (b) an alkenyl aromatic monomer; (c) a low profile additive; (d) a peroxide initiator; (e) a thickening agent; (f) fibrous reinforcement material; and optionally one or more components selected from the group of (g) mould release agents; (h) wetting and viscosity reducing agents; and (i) fillers, wherein the composition also comprises a uret dione diisocyanate, in an amount of at least 0.2-1.0% by weight relative to the total weight of components (a), (b) and (c) of the resin composition. The resin compositions according to the invention in particular have a low emission of volatile organic compounds (VOC). More particularly, the resin compositions have excellent Class A properties.