Explore Scientific 20mm 100 degree Series Nitrogen-Purged Waterproof Eyepiece. The Explore Scientific 20mm 100 Series Hyper-Wide Nitrogen-Purged Waterproof 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. The Explore Scientific 20mm 100 Series Hyper-Wide Nitrogen-Purged Eyepiece will have you forget that there's an eyepiece between you and the universe. Specifications for Explore Scientific 20mm 100 Series Hyper-Wide Nitrogen-Purged Waterproof Eyepiece: Focal Length: 20mm Length: 156mm Width: 70mm Weight: 38.1oz; 968g Barrel Size: 2.00" Eye Relief: 14.5mm Field Stop Diameter: 34.8mm Package Contents: Explore Scientific 20mm 100 Degree Series Nitrogen-Purged Waterproof Eyepiece Explore Scientific EPWP10020-01: 20mm 100 degree Series Nitrogen-Purged Waterproof Eyepiece