Male Jack Set features two male plugs.  Each has a 3/8" stud to plug into a welder or a female jack and a 1/2" ID hole to insert welding cable.  They also include plate & screw hardware as shown. 

Female Jack Set includes two female plugs.  Each plug has a 3/8" ID hole for male jacks & 1/2" whole for cable.  Female jack sets comes with set screws & plates.