Bohning's T Nock is great for wood, fiberglass, and swedged aluminum arrows. It's available in 1/4", 9/32", 5/16", and 11/32". The 1/4" throat size is .105" (2.67mm) and it weighs an average of 6 grains. The 9/32" throat size is .115" (2.92mm) and it weighs an average of 8 grains. The 5/16" throat size is .115" (2.92mm) and it weighs an average of 14 grains. The 11/32" throat size is .105" (2.67mm) and it weighs an average of 15 grains. Proudly manufactured at the Bohning Factory in Lake City, Michigan, United States.