Button head types have cylindrical heads with curved tops and flat bearing surfaces. They slightly protrude out of the workpiece and are used for aesthetic purposes.
Hex socket drive types have a hex-shaped recess in the head and are driven with hex keys or hex socket bits. The driving surface is protected from external damage and provides six sides of contact surface for added torque.
Stainless steel is a strong, corrosion-resistant alloy with excellent resistance to heat. It is used in high-stress, outdoor and corrosive applications.