They use the same inserts that they use in ST Epic's.There are no heavier inserts available and the inside diameter is not large enough for the screw-on weights like GT weights.They are a 9/32" carbon shaft,you would have to make your own.I have made some heavier inserts for my CX Heritage 90 that are 9/32".I took some 5/16" brass inserts and mounted them on a field point in my drill.I spun and filed them to fit the CX 90,it took a 50 gr. insert down to 42 grs.But made 5/16" points fit more flush without the little lip overhang.There is alot more point weight choices in the 5/16" size.Great quality shafts though are alittle on the expensive side.