The HMH Standard, Spartan, CX Cross-Over and ST Vises all have our famous interchangeable JAW option making these vises the most versatile of fly tying vises on the market. The MAGNUM JAW is designed for big hooks up to 6/0+. Simply unscrew the existing jaw from the vise and replace it with the Magnum. It's that simple. All HMH Jaws come with a lifetime Guarantee. Made in USA.