Knee breeches, used by most armies in the Napoleonic period for full dress, both for infantry and cavalry. The first ones pictured are for officers, with two side hip pockets, while generally those for other ranks (pics 5 and 6) had no side pockets, but only a small "watch" pocket on the waistband. Also, in many armies private soldiers' breeches had no knee straps for buckles but closed with either a tape string or button. In the French army, however, even private soldiers breeches had knee buckles (and often also a back waist buckle), which can be purchased separately.
These breeches can be made in wool cloth, or else linen, hemp or cotton for summer undress wear. Available in standard sizes but they will fit better if you take your own measures accurately, and fill in the form above.