LDB's remarks are almost exactly my own. The Aimpoint was the first really successful red dot. They are of excellent quality and expensive. The 1" Ultra-Dot is rugged, optically well made (i.e. reasonably parallax free) product that has found great favor with competitive Bullseye shooters. Prices are usually above $100 but under $200. The less expensive red dots typically have more parallax than Ultra-Dots or Aimpoints. Some really cheap Chinese made red dots will not stand up to the recoil and vibration of an auto-loading 22 RF.