BKL SMA and RP-SMA Connectors 50 Ohm Gold-plated – BKL 419021, BKL Electronics 0419021 SMA plug connecters are used mainly for applications in the frequency ranges 1GHz to 18/26.5GHz (depending upon the design). SMA stands for Sub-Miniature-A. The male SMA connectors have a central pin and an internal thread whilst Reverse SMA (RP-SMA) male connectors have central socket contact and an internal thread. They have a high mechanical strength owing to the 8mm screw lock. BKL 0419021 SMA Reverse Male PCB Mount Vertical 50 Ohm Gold-plated 17mm High