Integrated Headsets - hidden bearings
According to SHIS (Standardized Headset Identification System), in addition to EC (External Cup) and ZS (Zero Stack), there is also the option of connecting the fork and headtube with a fully integrated IS headset. IS stands for "Integrated Standard" and means that the bearing shells are permanently installed in the head tube and do not have to be pressed in by hand. In the integrated bearing shells, the bearings are simply inserted and can be removed just as quickly. Assembly and disassembly of the fully integrated headset is straightforward.