O-Ring Sold Separately: Ai # Sd6540-228 / Mfg # 6540-228Used In: 400, 600, 600S, 700, 750, 800, 850 1992 Suncoast, Suntub, Sv/DvReplacement Option For: Ai # Sd6600-105 / Mfg # 6600-105 Mfg # 6600-134 Mfg # 6600-138 Specifications Category: Thermostats / Sensors / Hi Limits Subcategory: Temperature Sensors 6600-167