One new old stock vintage authentic Switchcraft branded connector. Sometimes referred to as a "button plug" These have the nice old slightly darker Chrome finish. See pictures- Very sharp looking! Fits many old amplifiers, and mics including JT30 type harp mics. Heathkit and Eico test equipment also used these connectors Male or Female connector: Female as pictured, OR you can simply unscrew the outer ring and have an instant male connector! You can buy two and make yourself an extension cable this way. See our other listings for other versions and Amphenol brand of the same type. This is the standard size, Outer ring outer diameter is around 3/4" or 19mm , see our other listings for the smaller version