These adapters are for Wildcat shrouds that extend past the air tube and has female threads once you remove the front shroud cap. It is also compatible with FX Royale 400/500, Boss and Whisper. This adapter is Male to Male, one side is M20x1 that goes into the shroud and the other end is 1/2 x 20 UNF.
*Make sure to use a suppressor one caliber size up. Works really well and reduces the chance of pellet clipping.