FEATURE To Connect OWNV-10 Night Vision onto the Helmet. Made of Alu 6061-T6 Adjustable, 2 Pcs Combo, Flip-up-down Style, Light Weight, Easy of Use Check the video for installation illustration SPECIFICATION Diameter: 21.5mm 0.85in The 1st lever for clamping the cylinder mount The 2nd lever mount can control the damping force to flip up and flip down the monocular night vision The 3rd lever mount will lock the position between helmet and whole mounting system Weight: 130g / 4.6in Made of Alu alloy 6061-T6 Quick detach and release mount to the helmet 2 pcs combo, easy of use Check video for installation illustration VIDEO