Set screw shaft collars are the most effective when used on a shaft made of a material which is softer than the set screw. Ruland set collars are furnished exclusively with forged socket set screws for greater torque capacity and improved holding power. Forging of the stainless steel set screws has the additional benefit of work hardening, which results in stainless steel with elevated hardness and performance. Set screw shaft collars are made from 1215 lead free steel with a proprietary black oxide finish, 303 stainless steel, high-strength 2024 aluminum, and engineered plastic. Bore sizes range from 3/16" to 4" and 4mm to 50mm.