The OZ-06MS Leo is an MS developed using data from the OZ-00MS Tallgeese, which was the first combat MS to be created. Its most notable difference from the Tallgeese is that the Leo can be piloted by the average soldier. In addition to being highly productive and versatile, the MS can adapt to both ground and space units by changing equipment. Equipped with an abundance of armaments, such as the 105mm Rifle, Dober Gun and two types of Beam Rifles, the MS is supplied with various options for space and high maneuverability, and is able to cope with all kinds of missions.
During the "Mariemaia Incident" in A.C. 196, two Leo Space Types were seized by Heero Yuy and Duo Maxwell when they infiltrated the X18999 colony, and dealt a heavy blow to the enemy Leo forces. However, they were intercepted and defeated by Chang Wufei's XXXG-01S2 Altron Gundam and Trowa Barton's MMS-01 Serpent.