Tylok Fittings & Valves | 4,204 followers on LinkedIn. Manufacturer of instrumentation fittings and valves since 1955. | Tylok Fittings & Valves is one of the few instrumentation companies still proudly manufacturing products in the USA. Tylok remains an engineering company at its core, with an emphasis on innovation. In 1955, Cullen Crawford, known as father of the instrumentation fitting industry, founded Tylok.