Used for the .30 Cal. Phantom YHM-3300 and YHM-3300-Ti Sound Suppressors; Will NOT accommodate the 5.56 Phantom or Phantom M2 Sound Suppressors; Dual Support System supports and aligns the suppressor to your bore; 5-Port Design decreases visible flash; External Locking Mechanism keeps heat away from the spring mechanism; High-Temperature Spring holds up better over a longer service life; Threaded 5/8"-24; Shim Kit is included