Flush Mount Universal Stopper Cover With Horn, Custom Labeling, Blue Horn. These indoor/outdoor low profile or dome polycarbonate covers protect devices such as pull stations, keypads for entry systems, intercom stations, emergency buttons, electrical light switches, duplex plugs, etc., without restricting legitimate operation. The versatile cover offers excellent protection against physical damage (both accidental and intentional), dust and grime as well as severe environments inside and out.