Guidance device

There is disclosed a collar (100) which may be attached to a munition in order to control the trajectory of the munition. The collar (100) has a collar body (10); a surface (12) for capturing the projectile as it leaves the barrel; a sill (14) for supporting the surface (12) at the muzzle of the barrel; and a guidance means (20a, 20b, 21a, 21b) for altering the flow of air around the collar (100). The collar (100) supports itself at the muzzle and may attach to the projectile at the surface (12) to integrate with the projectile as the projectile is fired. The collar (100) is particularly suited for attachment to mortar rounds. Such a collar (100) gives a weapon operator the option of increasing the precision of a munition without having to carry a plurality of munition types.