Yeah the bolts on the OEM pipe stay on the pipe when ya remove it. The slip-on (if new) would have came with three new bolts (loose - not attached to the pipe in most cases). Since you don't have 'em, just buy something the same width as what's on the OEM pipe. Roughtly the same length too. Throw some lock-tight on em, and maybe check em every now and then to make sure they're tight since they're not the 100% right bolts. No harm at all.