The Aqua One Glass Thermometers are a must have accessory for any aquarium.The easy to read thermometers include a high quality silicon suction cup to fasten it in the aquarium. Both models are mercury free for added safety.Features & BenefitsEasy to readHigh quality silicone suction capTemperature range of 0-500Does not contain mercurySuitable for: Coldwater, Tropical & Marine