Use the Zhumell 2-inch 2x ED Barlow Lens with Compression Rings in conjunction with any eyepiece to effectively double your magnification. The ED optical lenses provide superior image quality and contrast, maximizing the starlight that reaches your eye. Other manufacturers employ standard optical glass in their Barlow lenses, which can actually decrease the amount of light that reaches your eye if improperly designed. Users of all experience levels agree that a 2x ED Barlow lens is one of the first accessories you should own for your telescope. This model fits both 2-inch and 1.25-inch format eyepieces.