Perfect for home or office use, this coupler allows you to connect two telephone handset cords together. Made with high density plastic and 24k gold plated contacts. Simple and easy to use, not tools are required. Each side has an RJ9 4P4C modular plug. Simply insert the handset cords into each end and now the cords are combined in length. Please note: these couplers are not for connecting line cords together, they are for handset cords. Line cords connect the phone base to the wall plug, handset cords connect the handset to the phone base. Handset cords are typically curly and line cords are straight.