A "microinch" is a unit of length used to measure extremely small distances or dimensions. It is equal to one millionth of an inch or 0.000001 inches. In scientific notation, it can be represented as 1 µin (pronounced as "one microinch").
Microinches are typically used in precision engineering, manufacturing, and industries where very fine tolerances and high levels of accuracy are required. This unit allows for the measurement of surface finishes, material thicknesses, and other minute details with extreme precision.
To put it into perspective, a microinch is much smaller than a human hair, which is typically several thousand micrometers (µm) or microns in diameter.
The term "long reed" does not refer to a standard unit of measurement or a widely recognized term in contemporary systems of measurement. It's possible that "long reed" is used in a specific context or industry, but it does not have a standard definition in general measurements.
If you have more context or specific information about how "long reed" is used, I would be happy to try to provide a more precise explanation.