Use this filler when you want an extremely high strength structural fillet that is very resistent to cracking, such as keel bedding and bonding hardware. This filler should also be used when the epoxy must fill a void, as the resulting mix is especially resistant to cracking. When mixing add an equal amount of Cab-0-Sil by volume to the mixed epoxy and then thicken the rest of the way with milled fibers. This mixture does not pull well but the Cab-0-Sil helps the epoxy to stay put when slow cure times are used. MAS recommends medium hardener with our FLAG resin when bonding and bedding.