This is a replacement input sleeve for the Getrag transfer case. If your input sleeve has worn splines, it must be replaced to prevent stripping the splines and the consequential costly failure of the central differential viscous coupling unit.
Installation requires a hydraulic press.
Buy as a package with a transmission output shaft and save $$$ money!
NOTE (for '91-92, 18-spline only): If the transfer case has a bolt in the middle of the cover near the "e" in "Getrag", then you need a "large bearing" sleeve. If no bolt then "small bearing".