The Spectre M4 is a submachine gun manufactured by SITES (Società Italiana Tecnologie Speciali S.p.A.) that chambers several different calibers. These calibers are the 9x19mm Parabellum, 9x21mm IMI, .40 S&W, and .45 ACP. Note: The Rainbow Six universe refers to the Spectre as the SM4 CQB. The weapon was later renamed the SP M4 in Lockdown. This does not count as a different variant of the weapon. The SM4 CQB is categorized as a submachine gun in the Rainbow Six universe. The SM4 CQB appears in Tom Clancy's Rainbow Six 3: Raven Shield and Tom Clancy's Rainbow Six: Lockdown.