The 13-sensor flex contains 13 TS4112 Light-to-Digital Converter ICs. The flex is made to connect to the Shoto HDK SteamVR Tracking rigid board.
Note: the 13-sensor flex does not come with the Shoto rigid board (see the Shoto SteamVR Tracking HDK for the complete tracking kit).
You can purchase the 13-sensor flex assembly individually to make multiple tracked object prototypes. The rigid Shoto board can then be shared between tracked objects as needed.