The new advanced light has 10 brightness levels, 5 individual LEDâ€™s for optimal brightness, auto off (after 4 minutes), allows you to light up your level and is 100% waterproof. To light up your level hold the power button for 2 seconds. The 5 LEDâ€™s brightly illuminate colored dots and fiber without the need for an up pin or big ugly battery packs with loose wires. Aircraft grade aluminum housing, anodized to a beautiful grey finish. Mounts onto Axcel, Shibuya, Sure-Loc, B3, CBE or any sight that accepts 10-32 threaded rods. Never run out of battery power again with over 6hrs of battery life at 80% brightness - takes two cr2025 batteries (can be found anywhere, common size). The inside diameter of the housing is 30mm. Easily swap from one lens cartridge to another depending on what discipline you are shooting.