All common forklift forks are produced in metric sizes, typically 4" wide are 100mm, 5" are 122mm, and 6" are 150mm translating into a finished size that is no more than what you expect. Typical thickness equivalents 1.25" are 35mm, 1.5" are 40mm, 1.75" are 45mm, 2.0" are 50mm, 2.25" are 60mm, and 2.5" are 65mm, so they tend to be thicker than you expect.
Example, if you have a forklift accessory with a 2.25" height and you're told your forks are 2.25" the forks actually could measure 2.36" or slightly thicker when you consider possible manufacturing tolerances. Square peg, round hole as they say.