Designed for use with SCHALLER strap locks (not included), the strong brass construction of Acousti-Lok provides you with the security you are looking for. With different Acousti-Lok designs to choose from, make sure you choose the one that is compatible with your acoustic guitar's output jack. Acousti-Lok is not designed for use with recessed or flush-mounted jacks. It fits all standard 3/8" x 32 plugs and is black in color.