Momentum TDT Carbon Arrow Shafts are incredibly strong shafts. Part of that winning formula is due to the unique Insert/Outserts included with every pack. These effective aluminum inserts are combined with an external jacketed brass sleeve to provide an incredibly strong reinforced point end. Tapped on the back end to allow mounting of GrizzlyStik Brass Weights for those wanting added weight. Please Note: GrizzlyStik Momentum TDT Insert/Outserts only fit GrizzlyStik Momentum TDT carbon arrow shafts. Available in 170, 240, 320, and 400 spine models. Please specify. Weigh approximately 70 grains each. Sold by the 6-pack. See all GrizzlyStik products