Ideal for use in confined areas where the head needs to be flush or below the surface Drive Type: Hex Socket; Head Style: Button Head; 18-8 Stainless Steel Allen Hex Drive Size: 3/16; Head size: .437" diam, .132" height Thread: 1/4-20; 3 inches; 25 Pieces All pictures represent actual product. A button head socket cap screw is a screw with a button head and hexagon drive for tightening with an Allen-style wrench. This screw carries a recessed internal socket drive to add strength. The 18-8 stainless steel material provides strength and offers good corrosion resistance in many environments. The material may be slightly magnetic. The button head is round with a low profile, short vertical sides and is suitable for light duty applications. The internal hex drive, also known as a hex-socket drive, has a hexagonal slot that requires an Allen key driver, also known as a hex key or Allen wrench. Socket cap screws are threaded fasteners that have a cap head with an internal socket drive for installing in areas with limited side clearance.