Hammers 1x30BK: This compact and lightweight electro sight is built with a highly visible fine 2MOA dot with a 40MOA circle illuminated in red. Anodized matte black finish. Great for use on revolver pistols, rifles, and shotguns. Illumination intensity has 11-level adjustments for use under all lighting conditions. Fully adjustable for windage and elevation. Standard 30mm main tube with quick flip-open lens caps. Included with the sight is a pair of 30mm vertical split rings for a Weaver base. The rings can also be used with other 30mm tube scopes. Features: Brand: Hammers Dot size: 2moa with 40moa circle Intensity level: 11 Eye relief: Unlimited Tube size: 30mm Sight overall length: 5 1/4inch with caps installed; 4 1/2inch without caps Mount center height: 23mm Battery used: CR2032 button cell Total weight: 7.4oz Package Contents: 1x30BK with rings Flip open lens covers (back and front as shown in the picture) Allen wrench Microfiber Lens cloth 1x 2032 Lithium battery NOTE: Be sure to install the sight on the scope base with the light control tower positioned at your left-hand side. The vertical split scope ring should be tightened at the bottom first, and then tighten the top screw.