What is a microinch?
A microinch (µin) is the inch with the SI prefix micro, meaning one millionth, so 1,000,000µin make one inch.
The microinch is mostly seen in surface finish. US drawings give a part's roughness (Ra) in microinches, and a typical machined finish is 63µin, or 1.6µm.
A microinch is a millionth of an inch, which is exactly 0.0254 micrometers or 25.4 nanometers. Outside the US surface finish is given in micrometers instead.
What is a US league?
A US league is three miles or 15,840 feet. The word comes from the Late Latin leuca, a Gaulish measure traditionally taken as an hour's walk.
The league was used for the distance between towns and for a ship's run at sea. The mile and the kilometer replaced it, and it now mostly turns up in older books. A US league of three miles is about 4.83km.