Socket shoulder (Stripper) bolts have a hex socket (Allen) drive and a cylindrical head.  The shank or shoulder on the top of the socket shoulder bolts have a smooth finish to allow for rotation of pulleys, linkages, and moving parts.  These bolts are commonly found in mechanical applications, engines, and moving wheels.  There are narrower threads underneath the shank/shoulder of the bolt.  The stripper bolt term is used when the bolt is attached to a stripper plate.  Steel and stainless options are available for the material and imperial and metric options are available for sizing.