The Z Series of right-angle gearboxes from STM, distributed by HMA Flow & Industrial, is designed for heavier-duty applications. The single-piece body is made from cast iron, with all of the external faces machined.

The gears are Gleason design, while the bearings are overrated as well. The high gear strength and case design results in a good relationship between power and overall dimension, meaning that the Z Series of right-angle gearboxes from HMA Flow & Industrial can also operate at high speed. The modular construction allows configuration with up to six input/output shaft variations (except ratio 1/1).