*The FastFire III puts an unmistakable red dot at the point of impact within your field of view, giving you an immediate advantage in speed and accuracy*With lightweight construction and durable design, the FastFire III can be used as a primary sight or paired on top of an existing sight.*Rely on the automatic brightness sensor to adjust to match the environmental conditions or choose one of the three manual brightness settingsWaterproof roof to keep the glass of your sight clean3-MOA/8-MOA bright red dot for fast target acquisitionChoice of automatic or 3 settings of manual brightness sensors to adjust to lighting conditionsWindage and elevation adjustments to make fine-tuning easy