Do not get the Ofna's. I just purchased them and made this mistake. I should have listened to the people here that told me to get Mikes Maximizer's.
The problem with the Ofna's is that the hex "points" (if you look at the picture) are rounded off for some reason. Pic....
http://www2.towerhobbies.com/cgi-bin...?&I=LXXE06&P=Z
The Maximizer's hex points are squared, Pic...
http://www.rc-monster.com/proddetail...er_2330&cat=42 therefore giving more "bite" inside the rim and less likely chance of stripping. Stripped mine after the second time out.