MMCX connectors are coaxial RF connectors that are similar to MCX but are smaller. They comply with the European CECC 22000 standard. MMCX connectors have a 500-cycle pairing rating. The connectors normally include a lock-snap mechanism that allows 360-degree rotation and a 50 ohm impedance. They can operate in a wide range of frequencies, from DC to 6 GHz. MMCX connectors can be found on Wi-Fi PCMCIA cards as antenna connectors, as well as connectors for external GPS antennas on tiny devices such as PDAs or GPS receivers, and on mobile phones to connect external GSM antennas. Different brands of in-ear monitors utilize them to connect the wire to the separate earpieces. This enables the cables to be switched or replaced. In the 1990s, they were created.