3 Types Dew Heater Strip 25/30/40CM 5V for Astronomy Telescope/Camera DSLR Lens Temperature Keep from Fog Dew Freeze This product is for defogging only.Hands are hard to feel hot. It takes a lot of patience to feel the heat. Features: 1.100% brand new and never used 2.DN25: the length is 25cm, for outside diameter: 8cm, lens UV size is less than 55mm 3.DN30: the length is 30cm, for outside diameter: 10cm, lens UV size is less than 72mm 4.DN40: the length is 40cm, for outside diameter: 13cm, lens UV size is less than 110mm 5.Dew heater strap is an essential accessory that protects your optical tube from excess moisture forming condensation on the corrector lens 6.Cloth covered with foam insulation on outer side for maximum efficiency and performance 7.Electrical interface: USB Power Bank is required for 2A 8.Voltage: 5V 9.maximum power: 10W 10.Width: 50 mm 11.USB cable length:52cm 12.Weight: 60g/2.11oz 66g/2.32oz 73g/2.56oz Package: 1 x DN25cm Dew Heater Strip or 1 x DN30cm Dew Heater Strip or 1 x DN40cm Dew Heater Strip