All of Val Cox Frit is made with premium furnace glass (96coe). The metal oxides that give furnace glass its intense colour also make it more elastic. This means that Val Cox frit is compatible with Moretti/Effetre/Vetrofond (104COE) and Bullseye (90COE) as long as you use it in moderation. A conservative rule of thumb is 5% of the weight of the bead. Fortunately, since furnace glass colours tend to be intense, a small amount not only works best, it looks best.