The FSA Big Fat Pig Reducer Headset incorporates a reduction design 1.5" sized headtube to 1 1/8" steerer. This threadless headset with forged chromoly cups benefits from 21mm headtube insertion super oversized " lower ball bearings chromoly crown race and aluminium top cap. FSA Big Fat Pig Headset Features Reduction design 1.5" sized headtube to 11/8" steerer. Threadless headset with forged chromoly cups 21mm headtube insertion super oversized Lower ball bearings Chromoly crown race and aluminium top cap. Replacement bearings 160-6730 x 2. Upper Stack height: 17mm Lower stack height:11.7mm Total stack hieght:28.7mm