Stt-1 Sonic Tension Tester. Designed to assist in the installation of belts on certain applications. Required for proper installation to avoid damaging the belt. Available separately so the technician isn’t forced to buy a tool every time a belt is installed, unlike the OE belt. Re-usable. As an engineering leader with a strong foundation in research and development, Gates is committed to advancing the science of motion performance by developing safe, forward-thinking products, services, systems, and solutions, as well as fostering long-term customer and employee relationships. Headquartered in Denver, Colorado, Gates employs over 14,000 people across 106 locations in 30 countries. If it moves you, there's a good chance Gates has a part in it. Gates. Powering Progress. We sell our products globally under the Gates brand, which is recognized by distributors, original equipment manufacturers, and installers as the premium brand for quality and technological innovation, a reputation which we have built.