If you are an ambitious camera flyer, the concentric is your best and most precise option when talking eyesights. The bull's eye center, allows the camera-flyer to track and target the exact focus of the image. Protected by two glass layers the proprietary crystal and polarizer sandwich is housed by a sturdy black anodized aluminum housing. The ringsight comes complete with a 1/4" detachable post. The Brent is the elite eyesight!