This tool should be used as a guide only. AlkydPrimer may not be an exact match for Marine Undercoat by but we have given the closest match we can. AlkydPrimer should do the same job and have similar properties but you should always read the technical data sheets for both AlkydPrimer and Marine Undercoat to be sure. Please see any notes to see any major differences and call us on 01285 862132 if you have any specific questions.