Different size isotope containers have different mixes of lead in them, so ask Jerry which kind that is, and if it needs anything in it before casting. In that ad, he says it is the "soft" isotope lead. 'Dunno what that means, but I'm shooting some isotope lead that is 95-2.5-2.5 and it is great just as is.
But I do know they make more than one kind of isotope container.
