I installed the FIT guards on my gasser and even using a different brand of bars (I believe they are "Fly") the inserts didn't work worth a darn. I'm pretty sure that I just used leftover bar inserts from from either my stock KTM or Cycra guards. If you want to really lock them in, try some threaded inserts like these:
http://www.highwaydirtbikes.com/HDB_...=Th_insert_tap