Murray space saving, plug in circuit breakers are intended for use in Murray load centers and meter combinations that are rated to accept type MH-T breakers. Check wiring diagram to confirm. To ensure the warranty on a Murray panel is not voided, the use of Murray breakers is required. The triplex breakers provide two single pole and one double pole breakers in half the space. These triplex, 1/2-Inch frame breakers are ideal when new circuits are required in a panel that has no available spaces. Murray strongly recommends against the use of "used" breakers. The installation of used breakers in a Murray panel will void the warranty on the panel. Murray does not sell used breakers and has not approved any 3rd party sellers to do so.