Yoshimura offered us special pricing on their original part # system for the Z125, and we took on limited inventory. This system is the identical Works system as the new part number, the only difference being it has the 12mm (stock size) sensor bung, where as the new part number system has a 18mm bung and 12mm reducer. For those not needing to build their own map with an auto tuner, this saves you $109.80, while inventory lasts. https://mnnthbx.com/product/yoshimu...z125-pro-v1-12mm-bung-fits-factory-02-sensor/