View source for Shell size

Foraminifera range in size from a few tens of micrometers to 20-30 centimeters. They are mostly microscopic, usually ranging from 0.1 to 1.0 mm. The small size of most foraminifera make them much more useful for biostratigraphic or paleo/environmental applications, petroleum exploration etc. than larger fossils  because there can be thousands of specimens in a small sediment sample.