The Celestron 2" Luminos Barlow Lens increases the magnification of your 2" and 1.25" eyepieces by 2.5x. The premium 4-element apochromatic optics are fully multi-coated for optimum light transmission and yield high contrast, true color images. The beautiful hard-anodized aluminum housing matches the eyepieces in the Celestron Luminos line. A centralized rubber grip helps to keep your hands securely on the barrel, even when your fingers are cold or you are wearing gloves. A brass compression ring just inside the top of the Luminos 2.5x Barlow grabs your 2" eyepieces gently but firmly when you turn the oversized thumbscrew. Once the thumbscrew has been secured in place, the brass ring keeps your eyepiece in the Barlow instead of relying on the tip of the thumbscrew itself, offering a better grip and protecting the barrel from scratches. A matching 2" to 1.25" adapter is included so that you can increase the magnification of all of your eyepieces, both 1.25" and 2", in this versatile Barlow lens. The insert barrel of the Celestron Luminos 2.5x Barlow is threaded to accept 2" filters. This is a nice feature, because you can change eyepieces without removing and reattaching the filter each time.