H4 valves and caps are replaceable, reliable, airtight and fully compatible with all the parts of H3 valves. The working parts of the H4 valve are in its outer portion, which makes it easy to clean the valve seal. The inner portion is totally enclosed, with fine holes that help block any debris inside the chamber from getting into the valve seal. The New Short Halkey-Roberts Fill Adapter and Halkey-Roberts Valve Wrench will work with this valve.