A. O. Smith’s Master-Fit Series 200 ultra-low NOx gas water heater, for sale only in California markets, includes two models: the 81-gal. BTL-198 at 65” tall and the 100-gal. BTL-199 at 73” tall. The series features increased accuracy and dependability of the control system, reduced excess heat from the burner, and improved overall reliability and longevity.