How big can we make the letters?
There is not limit to the size or length.   We can make up to a 29" tall letter or sticker.   Our 24" clock faces are cut all in one piece.  Larger pieces can be cut and pieced together to make any size you need.

How small?
We can go as small as 1/2" depending on the font you use.   A chunkier font works better at small sizes than a skinny font.
Tiny letters are harder to do and will probably cost more and create much whining and pulling of hair.