FX Wildcat/FX Royale 400/500 adapter #A12. This adapter is Male to Male, one side is M20x1 that fits into the shroud, other end is 1/2″ x 20 UNF. – Extension sits behind lower air tube – Compatible with FX Royale 400/500, Boss & Whisper *Note if you have a newer Wildcat, this is not the correct adapter. Correct adapter – FX Impact / Wildcat – 1/2x 20 UNF adapter, matte finish with thread protector