IMPACT performance series bits dont just work with impact drivers. They are designed specifically for them and the higher torque they produce. Reverse spiral flutes grip harder as resistance increases for maximum grip power. Constructed of premium high-carbon steel for durability and extended drilling life. Black oxide finish resists corrosion. Universal lobular design fits all types of fasteners. Square drive fits impact wrenches, or drills and impact drivers when used with included adapter. Size 3/8 square drive with 1/4 hex adapter.