An extension to USB includes an insulative tongue portion and a number of contacts held in the insulative tongue portion. The contacts have four conductive contacts and a plurality of differential contacts for transferring differential signals located behind/forward the four standard USB contacts along a front-to-rear direction. The four conductive contacts are adapted for USB 2.0 protocol and the plurality of differential contacts are adapted for non-USB 2.0 protocol. The extension to USB is capable of mating with a complementary standard USB 2.0 connector and a non-USB 2.0 connector, alternatively.