For bikes with semi-integrated ZS head tubes, the Ritchey Comp Semi-Integrated ZS headset stands out above all others.
Tapered version
Stack Height: 11.6mm
Material: Steel
Headtube ID upper : 44mm
Headtube ID lower : 55mm
Upper Fit (S.H.I.S.): ZS44/28.6
Lower Fit (S.H.I.S.): ZS55/40
Bearing: Semi Cartridge (SSC)
Verified weight without starnut