Button Head Bolt are recommended for high strength applications. Button and Flatheads are suggested when only moderate strength is needed. For Button and Socket heads, measure the length from under the head. For Flat heads, length includes head height
A socket cap bolts, also known as a socket head capscrew, socket screw, or Allen bolt, is a type of cap screw with a cylindrical head and hexagonal drive hole. The term socket head capscrew typically refers to a type of threaded fastener whose head diameter is nominally 1.5 times that of the screw shank (major) diameter, Forged heat-treated alloy examples are high strength fasteners intended for the most demanding mechanical applications, with special alloy formulations available that are capable of maintaining strength at temperatures in excess of 1000 degrees F (587ºC).