This is a TangoDown Cover, model IO-003FDE.
New and improved! Protect your T-1 lenses" and keep them clear of rain" snow" mud or dust. The iO cover has integral lens covers and a protective armor body that can't fall off or get lost. Low profile design allows covers to be quickly operated with one hand. Covers nest together so they don't flop under recoil. Receptive to most spray paints and hydro dip processes. Fits Aimpoint(TM) T-1/H-1/R-1 Optics
Features:
Protects lenses
One handed operation
Resists solvents oils and UV exposure