Explore Scientific 30mm 100-Degree 3in. Series Argon-Purged Waterproof Eyepiece. Series Argon-Purged Waterproof Eyepiece. The Explore Scientific 30mm 100 3" Series Hyper-Wide Argon-Purged Eyepiece features a field of view that is close to the maximum for hyper-wide with not just directly at an object but slightly to either side as well. With the Explore Scientific 30mm 100 Series Ultra-Wide Argon-Purged Waterproof Eyepiece you'll be able to observe even the faintest of objects in the night sky. Specifications for Explore Scientific 30mm 100 Series Ultra-Wide Argon-Purged Waterproof Eyepiece: Focal Length: 30mm Length: 200mm Width: 107mm Weight: 82.9oz; 2353g Barrel Size: 3.00" Eye Relief: 19mm Field Stop Diameter: 52.2mm Features of Explore Scientific 30mm 100-Degree 3in. Series Argon-Purged Waterproof Eyepiece: EMD Coatings 3-inch O.D. Telescope with a 3 in. focuser and a 3 in. diagonal is required. Package Contents: Explore Scientific 30mm 100-Degree 3in Series Argon-Purged Waterproof Eyepiece 100 Series 30mm 3-inch Argon-Purged Waterproof Eyepiece; 3.0-inch O.D.