As many as you can put in there pretty much. You want to get as much surface area of your barrel possible to be "spaced." I suggest the one piece wax spacer. Check out the guide for the LRB wax spacer and follow the instructions minus the wedge to bend the barrel. i also suggest when doing this that instead of using hot glue to plug the barrel, you instead use something like a cleaning rod wrapped in electric, or better yet teflon tape to act as a barrel plug/wedge. Saves you the trouble of getting the hot glue out.