Billet S400 oil drain flange to -12an / Jic 37 degree taper. If you are using less than this, it can cause oil to leak past seals.
10 AN S400 S300 EXTENDED OIL DRAIN FLANGE
Vibrant 28995 um Oil Drain Flange (w/Crowfoot) -10AN Male Flare 2.060in Bolt Ho
Aluminum Garrett / turbonetics Oil Drain Flange for GT25R/GT28R/GT30R/GT35R/GTX
Turbo Oil Drain Flange For G series G25 G30 G35 660 770 900 1050 8AN Aluminum
Aluminum Turbo Oil Drain Flange 10AN Garrett GT40 GT42 GT45 GT47