Explore Scientific 9mm 120 degree Series Argon-Purged Waterproof Eyepiece. The Explore Scientific 9mm 120 Series Hyper-Wide Argon-Purged Eyepiece gives you even more universal real estate but you also see the main attraction whether it is a nebulae a galaxy or a star cluster close up and personal. The Explore Scientific 9mm 120 Series Ultra-Wide Argon-Purged Eyepiece let's you see beyond the huge swath of the night sky and a whole new experience overall. Specifications for Explore Scientific 9mm 120 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 120 Degree Series Argon-Purged Waterproof Eyepiece 120 Series 9mm Argon-Purged Waterproof Eyepiece; 2.0-inch O.D.