Insulating/sealant plastic helps prevent electrolytic corrosion on jointing points between two different metals such as: aluminium fixed onto stainless steel screws, aluminium windlasses or brass fixed with stainless steel bolts, stainless steel accessories for mast fixed onto the mast itself (made of aluminium) with rivets or screws, cleats secured with different metal studs. Duralac is a yellow plastic based with barium chromate, flexible and resistant, to be fitted in between two metals that are jointed together; application with brush; do not dilute