Honeywell Aquastat Controller, Circulator Application, Immersion Device for Limiting or Regulating Temperature of Liquids, 3/8″ x 2 7/8″ Copper Bulb, SPST Contacts Break on Temperature Rise, Horizontal or Vertical Mounting, 100-240 Degree Operating Temperature Range, 1 1/2″ Capillary Length, 5 Degree Fixed Differential Temperature