Adapts the 2.7 focuser to the Tak wide mount T-ring. You will really want to purchase the Camera Angle Adjuster with this so you can rotate the camera body around the optical axis for framing your photographic target. No vignetting with prime focus on an FS-102, I havent tried it with a reducer yet. I feel this should be included with the Camera Angle Adjuster for the same price that the CAA currently sells. Takahashi likes to nickel & dime you to death on accessories.