Orvis PosiGrip Screw In Studs- Aggressive tunsten-carbide tipped screw-in studs that can be added to any wading boot with at least ½" of midsole depth. Sharp tip allows for quick and easy isntallation into felt or rubber outsoles. A must where maximum traction is needed. ¼" hex head screws. Adapter for power drill included. 20 studs per pack. Made in the USA.