Osprey&reg; 4x32 mm Duplex Reticle Riflescope Recoil tested at 50 BMG parameters (1000g/0.4-0.8 ms). Waterproof tested at 25 cm/40 degrees C for three minutes. Completely fog-proof, each unit is "purged" prior nitrogen injection for optimum performance Fog-proof tested at 20 degrees C for thirty minutes and removed to ambient. Each scope must completely clear in 2 minutes. Each scope is spin-centered for balance before leaving factory. No nonsense lifetime warranty /three day repair or replacement.