Can anyone tell me what size of insert I need to buy for my GOLDTIP'S XT'S 55/75's? I can't believe I don't have a spare! I have never needed any till now. The shafts have always came with them and I'm lost! I just fletched up a half dozen with the new NAP Quick Spin vanes and I must have misplaced the inserts. BPS has a big sale going and this is the excuse I need to go back!