If You Have a Garrett GT25r, GT28r, GT30r, GT35r series Turbocharger, then You Need a Garrett Ball Bearing Oil Restrictor. This Oil Restrictor Fits Directly into the Ball Bearing Cartridge, and Seals on the Ball Bearing Cage Dowel Pin.  This Fitting Has a -4 an Connection fitting to Adapt Directly To a -4 an Oil Feed line.

Here You Can Buy Garrett Ball Bearing Oil Restrictor.

Take Note:  This Fitting is for Garrett Ball Bearing Turbochargers Only. Restrictors Should not be used with any Single Ball Bearing Turbochargers Such As Turbonetics Single Ball Bearing Turbochargers, or any Journal Bearing Turbochargers. This Restrictor Does Work with Precision Ball Bearing Turbos That used GT30r to GT35r Garrett Center Cartridges (Doesnt fit 6262, 6266, ball bearing etc).