Applicable exclusively for the Gen-3 top cover. Due to prevailing market conditions and a significant surge in sales volume, orders are currently experiencing a shipping delay of 5-6 business days. We value your patience and continued support. This is a basic rear peep sight, non-adjustable, calibrated for a 100 yd zero. The aperture diameter is 0.07 inches. Fixed rear peep sight - a non-adjustable, basic aiming device designed for precision targeting, offering a simple and reliable shooting experience The firearm's sight has been precisely calibrated to achieve a zero at a distance of 100 yd The aperture has a diameter of 0.07 inches