The Pinnacle of Precision & Performance Altra Forward Mass System (FMS) micro insert weight system offers fine adjustment of total arrow weight to increase F.O.C. and improve down range accuracy. The micro insert weights are designed for use with all Altra 166 arrows and are stackable for infinite weight adjustment.

Features:Comes in 12 pk QTY;Available 10 & 20 Grains;Blue Loctite recommended for assembly