The Burris FastFire E is a red dot sight with a 3.5 MOA dot. It comes with an Aimpoint ACRO footprint adapter, so it mounts on slides and plates cut for the ACRO. If your slide is cut for an ACRO but you don't want to pay Aimpoint ACRO money, this is a budget option that is mechanically compatible. A 3.5 MOA dot is small enough for precise shots at distance and still quick to pick up up close. The housing is aluminum, and the sight runs on a common CR2032 battery. Optical quality and durability are a step below the Aimpoint, but the mount pattern matches. Specs: Reticle: 3.5 MOA red dot Housing: aluminum Footprint: Aimpoint ACRO (via the included adapter) Battery: CR2032 Finish: black Confirm your slide or plate is cut for the Aimpoint ACRO footprint before you order. It will not fit RMR, RMSc or Docter cuts without a different plate. Mount it with the adapter, torque the screws evenly, and zero the sight before you rely on it.