Help prevent condensation from building up on your delicate lenses when working outside with the Vixen Optics Lens Heater 360 III. The 1.2 x 23.6" heated sheet gets wrapped around your telescope or spotting objective lens, eyepiece, or camera lens less than 3.9" (100mm) in diameter by sending a low current through the soft non-marking or marring felt-like material. Its low 3W power consumption ensures it won't drain your external battery pack when you're out in the field and plugs into power supplies using the included USB cable.