The Bohning Blazer Double Lock F-Nock has the same double lock throat system as the time tested Blazer Double Lock Nocks. This throat system will keep your nock and arrow shaft on your string during let-down but will maintain a clean release. These small, press fit nocks are designed for "D" loops and strings shooters, as well. These nocks are made of a durable, impact resistant polycarbonate material so they will stand up to thousands of shots. The F-Nock series is designed to fit Easton CB Uni-Bushing ("G" nock) or other "G" sized arrow shafts.