The entire Copeland/Optec Retinoscope is adjustable for preferred eye alignment. Streak revolves 360 degrees without stops. Width of streak is controlled by smooth up and down action of thumb slide. Instrument includes Rechargeable Power Insert with improved electrical system. Available in newer 3.6 volt Halogen, or standard 2.4 volt system. The "A" type power insert fits American Optical/Reichert charging wells, while the "B" type insert fits Welch Allyn, Bausch & Lomb, Reliance, or Marco wells.Please Note: Copeland Streak Retinoscope has been discontinued. We recommend: Keeler Combi Streak Spot Retinoscope or Welch Allyn 18245 Retinoscope.