This replaces the brass slotted cap that often seizes solid, this is due to electrolytic action caused by the aluminium and brass reacting (disimilar metals). The use of PTFE on the thread can help to reduce this. The large useless slot is also replaced by a 10mm AF hex which uses a standard allen key. The cap has a recess to take a Nitrile 70 rubber seal which can be uprated to Viton if required.
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