2-3/8" EUE Crossover Left hand Pin X Right hand box EUE 2-7/8" Material 4140 Cross over subs act as an intermediary between two dissimilar threads and are used to connect the two. A cross over sub can also be used to protect other tooling in your drill string and since the cross over sub (also known as saver sub) is the least expensive item in the drill string it can be designed to wear before any other drilling component does. A cross over sub can be used just above the bit or in a reverse circulation application to deliver outgoing air to the bit face. In these applications a cross over sub is usually called a bit sub. Often times cross over subs will be phosphated to thread together easier. In addition, all of the WDT cross over subs can have wrench flats milled into them to allow for better assembly and disassembly.