FACT weight system wrench allows you to install or remove FACT weight screws into the back end of matching Gold Tip inserts already installed in the arrow, offering ultimate customization and tuning. Simply remove the nock, slide the weight(s) (sold separately) into the shaft, thread forward, and then use this long wrench to turn them into the back of the insert. Helps achieve the 8-12% Front of Center (FOC) recommended for most hunting applications.FeaturesTwo size options for different shaftsStandard for all .204 I.D. shafts and larger.166 Wrench for micro diameter shafts.