Twin Industries Extender Cards, Prototyping Boards, and Development Tools have accelerated hardware development for over 30 years. Come with the latest flexible printed circuit board materials and connect rigid/solderless boards. Battery Holders with machine pin jumper wires support AAA batteries and feature an ON/Off switch. Combines standard prototyping boards with solderless breadboard modules. Designed for easy insertion and extraction in solderless breadboards and other development boards.