You may be able to use the 283B-PL or 284B-PL instead if you only need fixed temperature. Earlier detection may be obtained by reducing the spacing between detectors. (See NFPA 72, Chapter 5) Detector twists and locks onto mounting plate. The heat detector is available with a white plastic reversible mounting plate. Mounting plate may be surface mounted or mounted onto any 3 1/4″ (83mm) or 4″ (102mm) octagon box.NOTE: Effective July 1, 2015, the 281B-PL and 282B-PL detectors will no longer be manufactured.