This tool should be used as a guide only. Jotamastic 80 may not be an exact match for Epomarine EX21 by but we have given the closest match we can. Jotamastic 80 should do the same job and have similar properties but you should always read the technical data sheets for both Jotamastic 80 and Epomarine EX21 to be sure. Please see any notes to see any major differences and call us on 01285 862132 if you have any specific questions.