Chief's CPAC501B is a M and P-series in-wall swing arm accessory, designed to hide a swing arm mount in the wall, taking installations to an even lower profile. Compatible with the PNRIW, PWRIW, MWRIW swing arms. Features large conduit knockouts for easier cable integration are compatible with metal single gang boxes. Saves installation time when used with a pre-assembled Chief in-wall swing arm. Takes a Chief on-wall arm and makes it in-wall for the ultimate flush appearance. UL listed.