Facial grammar, classifiers, and verbs are used to describe a distance of something. The major mouth morphemes to describe distances are: "AAH", "MM", "OO".
Some examples below will show you how to use mouth morphemes for distances.
The mouth morpheme "mm" conveys a meaning for a medium distance, a middle size, or an average.
Gloss: [t]ball[t] (ix-me) throw lcl-pathline.
A ball (object) is first topicalized with the raised eyebrows. The verb predicate contains the verb throw and its locative classifier (LCL) which describes the pathline and the direction of the ball.
The verb phrase accompanies with the mouth morpheme "mm". The distance of the ball being thrown is average, not too close nor too far.
The mouth movement "aah" conveys something that is far, moving far away, etc.
The signer uses the mouth shape "aah" to describe how far the ball is traveling from the origin.
The signer uses the "ahh" mouth movement to describe a very long line-up.
The mouth movement "oo" conveys a meaning for a short distance in some cases. Another mouth movement "cs" also describes a short distance (in either space or time).
Some ASL signs can use "cs" but cannot use "oo" and some vice versa, depending on what contexts are. Some ASL words can work with either "cs" or "oo" -- for example, by-hairline.
The mouth classifier "cs" signifies too close or extremely close either in space or time. Usually much shorter in distance than the mouthing "oo". For example, just right around the corner, right next to, just-recently, etc.
The signer describes how the ball is thrown weakly. Not only the signer uses the mouth movement, but also describes the relative distance by moving the hand between the ASL noun and the destination.
Not only these mouth morphemes are used to describe a distance in space or time, but they also describe other things than distance.
For example, when using sensitive while mouthing "CS", it's inflected to very-sensitive.
Also see facial grammar describing sizes: OO, MM, CHA