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 18265ghz 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