The MagView B1 Digiscoping Binocular Adapter is a versatile accessory designed for use with 38.5mm-43mm eyepieces. This adapter allows you to attach your smartphone or tablet to your binocular for easy viewing and capturing of images through the lens. With a weight of only 0.51 pounds, it is lightweight and easy to handle, making it a convenient addition to your binocular or telescope setup. Compatible with a universal range of brands, the MagView B1 adapter is a must-have for any birdwatcher or stargazer looking to enhance their viewing experience.