Usage Tips:[Mini Aquarium Heater] This small aquarium heater is only 5cm (1.97 inches) in length, takes up less space, and is easy to hide in the fish tank. the temperature range of the English Celsius model is 18°C-34°C. Please purchase according to your needs. [USB Powered Tank Heater] This heater is powered by a 5V/2A USB power supply, which is very safe. No need to worry about the fish getting electrocuted. Please use a 5V/2A power adapter (not included) or a 5V/2A power bank (not included) to power the heater. [Precise Temperature Display] Using smart inverter technology, this thermostat maintains the heater at a constant temperature through a built-in chip, which is more precise than knob control of the heater, and the display is easy to read the temperature. [Overheating Protection and Power-off Memory Function] When the water temperature exceeds the maximum temperature range, the fish tank heater will stop working. The heater will remember the temperature setting, and in the event of a power outage, when the power is restored, the heater will follow the last setting. [Widely Used] This fish tank heater is very suitable for small fish tanks of 1-5L. Can be used in fresh and sea water, it can be used not only as an aquarium heater, but also for turtles, pet fountains and plant seedlings. Please check as much as possible to make sure the item is what you need. Tips: The product may be updated constantly ,Due To Different Batches, The Actual Product May Have Slight Differences Or Color Differences, Which Does Not Affect Use Colour:Black Material:Plastic Package Contents: 1 x Fish Tank Heater Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.