Our e-dot sights use the same technology employed by fighter aircraft to achieve fast target acquisition. The 30mm Compact Model (ECB) is a versatile sight for a variety of shooting sports. It fits 3/8 inch or 7/8 inch mounts. With our parallax-free system, a red dot on the lens is super imposed on the target. Aiming does not require lining up the front and rear sights. Also, there is no need to center the dot. After sighting in, if you see the dot on the target, you're on target! The 1 inch model shares most of the same features as ADCO's premium line sights. The 1 inch format has always been our best seller. The dot can be changed from red for bright sunlight to green for low light conditions.