Normal Market Size

What Does Normal Market Size Mean?
A share classification structure based on the number of shares outstanding. This determines the number of shares that a market maker can trade at the quoted price.

Investopedia explains Normal Market Size
Buying or selling in amounts above the set number of shares requires price negotiation with the market maker. The NMS system reduces the effect a market maker's trading activity may have on the share price of a stock that has shares outstanding in the low thousands.