The clicksof the front and rear sight are calibrated for 1 MOA (3 cmat 100 m), allowing for a wide vertical and horizontal rangeof adjustment (240 cm at 100 m) and easy sighting-inof the scope. These sights require no batteries and thusare always ready for use. Corrosion-resistant Mil-specmaterials and raised sides protecting the ghost ring andfront sight from impact damage ensure many years oftrouble-free service. ERATAC Backup-Sight w/Red Fiber-Optic Insert