2.5x - 2" - Luminos Barlow LensThe Celestron 2. 5x Luminos Barlow increases the magnification of any 2 or 1. 25 eyepiece by two and a half times High quality 4 element optics produce a flat field for sharp images that are free of extraneous color Hard anodized aluminum barrel is threaded to accept 2 filters A brass compression ring holds eyepieces firmly in place, and large thumbscrews are easy to turn, even with gloves on A 2 to 1. 25 adapter is included. Allows the use of both 2