A20. 12x1 female spigot left medium shaft
Links to photos of examples:
Benelli G2 The valve shaft sticks out of a small hole in the plastic side cover. The black handle knob must be pried off (with two screwdrivers on opposite sides), to get the shaft through the hole in the plastic side cover. The valve must be aimed just right. It might take 2 or 3 guesses to get the shaft aimed at the hole. Then the plastic cover is replaced, and then the handle knob is pressed back onto the shaft.