Semi-integrated headset (zs) with steering stop for frames with 56mm head tube at the bottom. The Acros blocklock-zs56-headset-lower-part protects your top tube and down tube from contact with handlebars, attachments and the fork crown as well as the wires and cables from overstress in case of a crash. Compatible with all forks with a 1.5" steerer tube (40mm) at the bottom.