The HM46 Series is the same design as the HM45, but also incorporating a vent valve allowing a technician to perform instrument bleed or blowdown procedures. Both models provide one compact valve assembly to perform the block and equalizing functions required to calibrate your instruments. They feature backseated, inside rising stem construction to prevent accidental stem removal and to isolate the packing from the process. For added protection, the bonnets are pinned to prevent inadvertent removal.