Start with the side profile. A highball is the tall tumbler; a lowball is the shorter one. These names help identify the shape, but neither states an exact capacity.
If you want a tall and a short glass in the same range, label one drawing “Highball” and the other “Lowball.” Put each glass’s height, rim diameter and required capacity next to its own outline if those figures are known.
Write the unit beside each measurement. A height marked in millimeters and a capacity marked in milliliters are easier to read than two numbers without labels.
If the glasses need to look like a pair, identify the shared detail. For example, tell us whether to keep the same rim outline or follow the same side profile while changing the height.