A formulation for preparing a polyurethane foam comprising (a) a polyol component including at least (i) from 1 to 40 wt%, based on the polyol component, of a first polyether polyol, having a hydroxyl value from 25 to 30, a nominal functionality of 3, and a molecular weight of from 5000 to 7000 g/mol, the first polyether polyol being prepared from propylene oxide capped with ethylene oxide, having from 70 to 90 wt% primary hydroxyl groups; (ii) from 10 to 60 wt%, based on the polyol component, of a second polyether polyol, having a hydroxyl value of from 25 to 30, a nominal functionality of 2, and a molecular weight of from 3000 to less than 5000 g/mol, the second polyether polyol being prepared from propylene oxide capped with ethylene oxide and having from 80 to 98 wt% primary hydroxyl groups; (iii) from 2 to 7 wt%, based on the polyol component, of monoethylene glycol, 1,4-butanediol, hexanediol or neopentylglycol as a chain extender; and (iv) from 25 to 65 wt%, based on the polyol component, of a copolymer polyether polyol having a styrene acrylonitrile solids content of at least 40 wt% and an average hydroxyl number of at least 18; (b) an isocyanate component, comprising a prepolymer having an isocyanate equivalent weight of from 180 to 300, prepared by reacting a monomeric 4,4' diphenylmethane-diisocyanate and an isocyanate-reactive component; and (c) water as a blowing agent. (a) a polyol component including at least (i) from 1 to 40 wt%, based on the polyol component, of a first polyether polyol, having a hydroxyl value from 25 to 30, a nominal functionality of 3, and a molecular weight of from 5000 to 7000 g/mol, the first polyether polyol being prepared from propylene oxide capped with ethylene oxide, having from 70 to 90 wt% primary hydroxyl groups; (ii) from 10 to 60 wt%, based on the polyol component, of a second polyether polyol, having a hydroxyl value of from 25 to 30, a nominal functionality of 2, and a molecular weight of from 3000 to less than 5000 g/mol, the second polyether polyol being prepared from propylene oxide capped with ethylene oxide and having from 80 to 98 wt% primary hydroxyl groups; (iii) from 2 to 7 wt%, based on the polyol component, of monoethylene glycol, 1,4-butanediol, hexanediol or neopentylglycol as a chain extender; and (iv) from 25 to 65 wt%, based on the polyol component, of a copolymer polyether polyol having a styrene acrylonitrile solids content of at least 40 wt% and an average hydroxyl number of at least 18; (i) from 1 to 40 wt%, based on the polyol component, of a first polyether polyol, having a hydroxyl value from 25 to 30, a nominal functionality of 3, and a molecular weight of from 5000 to 7000 g/mol, the first polyether polyol being prepared from propylene oxide capped with ethylene oxide, having from 70 to 90 wt% primary hydroxyl groups; (ii) from 10 to 60 wt%, based on the polyol component, of a second polyether polyol, having a hydroxyl value of from 25 to 30, a nominal functionality of 2, and a molecular weight of from 3000 to less than 5000 g/mol, the second polyether polyol being prepared from propylene oxide capped with ethylene oxide and having from 80 to 98 wt% primary hydroxyl groups; (iii) from 2 to 7 wt%, based on the polyol component, of monoethylene glycol, 1,4-butanediol, hexanediol or neopentylglycol as a chain extender; and (iv) from 25 to 65 wt%, based on the polyol component, of a copolymer polyether polyol having a styrene acrylonitrile solids content of at least 40 wt% and an average hydroxyl number of at least 18; (b) an isocyanate component, comprising a prepolymer having an isocyanate equivalent weight of from 180 to 300, prepared by reacting a monomeric 4,4' diphenylmethane-diisocyanate and an isocyanate-reactive component; and (c) water as a blowing agent.