Ritchey:

The Ritchey Comp Cartridge Semi-Integrated ZS Upper Headset features full complement stainless steel angular contact cartridge bearings packed with Ritchey high-webbing grease.

Material: alloy
Stack height: 10.1, 15.2mm
Headtube ID: 44mm
S.H.I.S.: ZS44/28.6 (1 ?)
ZS44/28.6 (1 ?) bearing: 41.0/30.15/7mm 45/45 – sealed cartridge (ACB)
Top cap included
Weight: 51g
Colour: black