Dew heater with 30 cm strap is designed to fit 3” DSLR lens or telescopes. Works with 5V power supply and produces 6W of power.Equipped with standard USB plug to be powered from a USB power bank. Comes with 2m silicone cable. The strong Velcro strap makes it easy to wrap it around your telescope and hold it in place.Note! The OTA size is only estimated. Please check your OTA circumference before buying. Not to be powered by a laptop.