Explore Scientific 9mm 100 degree Series Argon-Purged Waterproof Eyepiece. The Explore Scientific 9mm 100 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. Explore the vast universe without actually leaving home with the Explore Scientific 9mm 100 Series Ultra-Wide Argon-Purged Eyepiece to give you that up close experience. Specifications for Explore Scientific 9mm 100 Series Ultra-Wide Argon-Purged Waterproof Eyepiece: Focal Length: 9mm Length: 145mm Width: 60mm Weight: 21.2oz; 602g Barrel Size: 2.00" Eye Relief: 12.5mm Field Stop Diameter: 15.7mm Package Contents: Explore Scientific 9mm 100 Degree Series Argon-Purged Waterproof Eyepiece 100 Series 9mm Argon-Purged Waterproof Eyepiece; 2.0-inch O.D.