The HHT series is Aventics' heavy-duty Numatics-heritage NFPA cylinder line — steel-body construction engineered for high-pressure, high-shock industrial duty in bores from 1-1/2" through 6" and beyond. Tie-rod assembly with steel tube and oversized internals supports working pressures up to 250 psi with the durability heavier process and metalworking duty demands. The HHT platform serves North American applications where standard aluminum-body NFPA cylinders won't survive — stamping, forging, and primary metals environments.