This tool should be used as a guide only. AlkydPrimer may not be an exact match for SD Primer S 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 SD Primer S to be sure. Please see any notes to see any major differences and call us on 01285 862132 if you have any specific questions.