Abstract: Light beam deflection means particularly for range compensation apparatus in weapons training aids for altering the angle of inclination of a beam of light to a selected value, comprising a pivotally mounted mirror positioned to reflect the beam of light, a cam movable to a position dependent upon the selected inclination, a cam follower engageable with the cam, an L-shaped arm interconnecting the cam follower and the mirror, and a stop movable between an operative extended position in which the stop acts to retain the mirror in a datum position, irrespective of the position of the cam, corresponding to a datum inclination of the beam, and a retracted position in which the cam follower engages the cam in such manner that the mirror occupies a pivotal position which reflects the beam of light at the selected inclination.