The silicon microstrip tracker was located just outside the Tevatron beam pipes. Five barrels concentric with the beams and 16 disks with strips perpendicular to the beams provided precision measurements of charged track coordinates. These helped to determine particle momenta and to distinguish those particles that emerged from the primary collision point from those that traveled a finite distance before decaying, like tau leptons and hadrons containing bottom quarks. It consisted of about 800,000 silicon strips of 50 micron width, capable of measuring track location to about 10 microns. The outer radius of the silicon detectors was limited to 10 cm due to their high cost. The silicon microstrip tracker was installed in the detector for the Tevatron Run II collider program, which began in 2001. It was fully functional by April 2002.