Explore Scientific 24mm 68 degree Series Argon-Purged Waterproof Eyepiece. This eyepiece from the specialists at Explore Scientific uses advanced computer design combinations of low dispersion and high refractive index optical glasses and durable multilayer deposition coatings. The Explore Scientific 24mm 68 Series Hyper-Wide Argon-Purged Eyepiece is impervious to internal fogging and contaminants such as fungus growing in between the lens elements. As a bonus the Explore Scientific 24mm 68 Series Ultra-Wide Argon-Purged Eyepiece is Argon-purged and waterproof to remain as pristine as the day it was assembled. Specifications for Explore Scientific 24mm 68 Series Ultra-Wide Argon-Purged Waterproof Eyepiece: Focal Length: 24mm Length: 75.6mm Width: 56.2mm Weight: 11.6oz; 329g Barrel Size: 1.25" Eye Relief: 18.4mm Field Stop Diameter: 27.2mm Package Contents: Explore Scientific 24mm 68 Degree Series Argon-Purged Waterproof Eyepiece 68 Series 24mm Argon-Purged Waterproof Eyepiece; 1.25-inch O.D.