The Suburban Mfg 525024 Furnace Low Air Flow Switch is designed for use with the Suburban Furnace NT-30/ NT-34/ NT-30M/ NT-34M/ NT-30S/ NT-34S/ NT-30SP/ NT-34SP/ NT-25/ NT-30/ NT-35/ NT-35K/ P-30S/ SF-20/ SF-25/ SF-30/ SF-35/ SF-20F/ SF-25F/ SF-30F/ SF-35F, and is sold individually.