T8 tombstone, use this socket for existing or new t8 tube installation. The T8 socket is shunted meaning both terminals are shorted together. Shunted are shorted between both sides of the end cap. Shunted for use with workhorse ballasts since the ends of the lamp are shorted. Non shunted is for use with advanced/universal because you have one wire to each terminal of the lamp, they are not jumped together. CE and Rohs certified. Comes as a pair (2).