Tapered-Socket Radiator Bleed Key
A winged radiator bleed key. The socket is a square that tapers from 6.6 mm at the mouth to 4.4 mm at the bottom, 11 mm deep, so it wedges onto any square bleed-valve spindle in that range instead of relying on one guessed size. The part is 64 x 16 x 24 mm: a gusseted 18 mm barrel on a flat wing that takes the turning load along its layers, plus a 5 mm keyring hole so the key stays with the boiler.
home radiator bleed-key heating