The width of feeler gauges does not vary much. The exception is when blades are tapered or custom made with smaller widths for easier placement in tight locations.
A feeler gauge that is considered short may have blades 12.7mm (½”) wide and 75mm (3″) long.
Short blade gauges are common and have a large variety of applications.
The length of blades do vary considerably. This is because extra length may be needed for difficult to reach applications.
A feeler gauge considered long may have blades 12.7mm (½”) wide and up to 600mm (24″) long.
Long blade gauges are often used to set air gaps between the stator (stationary part of a rotary system) and rotor in electric motors and generators.