Accurate Measurement of Water Temperature with Low/High Temperature Alert Preprogrammed for Tropical Fish & Clock for your Convenience. When Alert is turned on it will beep and flashes the LED lights if temp drops below 75 or above 82 For Salt or Freshwater Use - 3' Cord with All Plastic Probe & Suction Cup Dimension:L 2 2/3 " - H 1 2/3". Info from Oscar Ent.