Features: 1. This product is a heating defogging belt for astronomical telescopes and camera lenses with stepless temperature control. (Astronomy enthusiasts usually take pictures of the starry sky at night with large temperature differences in the wild. The objective lens of the telescope is prone to fogging similar to glasses. Play the role of heating and temperature control to prevent fogging, the same principle as the camera lens). 2. The length of the three models of this product is 25cm for the lens outer diameter of 8cm, UV lens less than 55mm; 30cm for the lens outer diameter of 10cm, UV lens less than 72mm; 40cm for the lens outer diameter of 13cm, The UV lens is smaller than 110mm. 3. Some smart power banks have smart detection functions, which will automatically power off after being switched on and cannot be used. The current requirement of the power bank is: 2A. Specification: Length is 40cm, suitable for lens outer diameter 13cm, lens UV size is less than 110mm The dew heater belt is an essential accessory to protect your optical tube from excessive moisture formation and condensation on the correction lens The cloth is covered with a foam insulation layer on the outside for maximum efficiency and performance DN25:the length is 25CM, for outside diameter: 8 CM, lens UV size is less than 55MM Width: 50 mm Power: DH25 - DH40 (< 10W) Voltage: 5V adapter: USB Power Bank is required for 2A Packing list: 1*Dew Heater Strip