Dew Heater Strip for Telescopes, Camera DSLR Lens, Telescope Eyepieces or other Devices -Keep them from Fog Dew Freezing Fits 3 Telescopes , 75mm Telescope - Tubes Outer Diameter From 80-112mm (3.15"- 4.4") Electrical interface: DC5.5*2.1(Female ). Cloth covered with foam insulation on outer side for maximum efficiency and performance Compatible with standard dew heater controllers such as Kendrick and others Dew-Not Dew Remover is a thick film heater manufactured for operation at 12 volts