The flip-open caps for the eyepiece and the objective lens are a modern solution that effectively protects the hunting optics against scratches, dampness, dust and impacts. The flip-open cap is locked and opened with only one finger, so it is practical to use. The opening lever is very quiet, it's the most open flip-open cover on the market! In addition, it is waterproof and does not crumble at low temperatures (made - elastic ABS plastic) The size of 39.4 mm is compatible with the following eyepiece riflescopes: Delta Optical Titanium: • 2.5-16x50 4A, 2D • 2.5x15.5x56 • 4.5x30x50 MCZ II, 4A • 4.5-14x44 • 4-16x42 • 6x24x42