This tool should be used as a guide only. Seaforce 90 may not be an exact match for Sigma Alphagen 650 by but we have given the closest match we can. Seaforce 90 should do the same job and have similar properties but you should always read the technical data sheets for both Seaforce 90 and Sigma Alphagen 650 to be sure. Please see any notes to see any major differences and call us on 01285 862132 if you have any specific questions.