This Green female receptacle is an easy and quick solution to putting a polarized plug on SPT-2 zipcord. Making your own extension cords with our xip cord using these plugs or using them to create custom C7 or C9 based light stringers is a snap. Also known in the industry as vampire plugs, this green female receptacle simply slips over the end of a cut cable. Slide on the cover, you've connected the receptacle to the wire and you're good to go.