Check the listing for details. system sensor B224RB 6" Mounting Base with Built-in Relay. Condition: New – Open box. Listed at 42.99 USD. this is nos - 'New Old Stock' generally refers to a 'lot' or 'bulk' item(s) that have been discovered tucked away from an old store or business. the box is in rough condition - The B224RB is a 6” plug-in detector relay base with a built-in form C relay for control of auxiliary functions such as elevator recall and door closure.One form C contact relaySupport for Class A and Class B wiringPlug-in mounting provides ease of installationTamper-proof feature prevents removal of the detector without the use of a toolRange of mounting options to meet any applicationask other questions you have!! shoes are sold on consignment so i have to go by the sellers asking price. i do understand shipping costs are high now and i do go by the post office prices. for heavy items please send your zip code and i can check for a cheaper rate through fedex. i ship mon-fri.