Three-speed Temperature Control: This lens dew heater comes with three-speed temperature control of high temperature about 55°C (131°F) ~65°C (149°F), mid-range temperature about 45°C (113°F) ~55°C (131°F), and low temperature about 35°C (95°F) to 45°C (113°F). USB Port Design: It's very easy to use because you can connect it to a portable power supply or any other power supply with a USB port. Safety Protection: Protect your digital camera lens or viewfinder from freezing due to cold fog and dew, allowing the device to work well at night where temperatures drop or weather is inclement. Hook and Fastener: The defogging band is secured by hook and fastener, which not only allows the defogging band to fit your lens, but also allows you to quickly detach and adjust the length you need. Wide Range of Application: This dew heater is adjustable in diameter and easy to stick, suitable for most sizes of telescopes, viewfinders, digital cameras, etc.