The Plasti-Bond 4" Knockout Hub PRST10 is a rigid metal conduit fitting with a gray color and a 4-inch diameter. It is made of metal and is designed for use with rigid metal conduit. With its rigid flexibility, this product is ideal for electrical equipment and supplies in the business and industrial sector. Whether you need to secure wiring or tubing, this knockout hub provides a reliable and durable solution for your conduit fittings needs.