Abstract: The invention relates to unsaturated polyester resins with higher molecular weight, low viscosity and high solubility specially in reactive diluents. The invention also relates to a method for the manufacture of such unsaturated polyester resins and to use thereof in various applications such as gelcoats. The unsaturated polyester resin comprises 20-85 wt % of at least one unsaturated polyester having a molecular weight of 2000-6000, prepared from 1) 30-70 mol %, preferably 40-60 mol % of at least two carboxylic acids or derivatives thereof and at least one of them is an unsaturated carboxylic acid or a derivative thereof and at least one of them is an aromatic carboxylic acid or a derivative thereof and optionally of one or more carboxylic acids and derivatives thereof, 2) 30-70 mol %, preferably 40-60 mol % of at least two diols and at least one of them is 2,2,4-trimethyl- 1,3-pentanediol and/or 2-butyl-2-ethyl- 1,3-propane-diol the amount of which is 0.5-8 mol %, preferably 2-6 mol %, 3) 0.