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