A 2ml microcentrifuge tube typically has a capacity of 2 milliliters, which means it can hold up to 2 milliliters of liquid volume. In terms of physical size, these tubes are generally small, cylindrical tubes usually measuring around 10-12 mm in diameter and 40-50 mm in length. They are commonly used in laboratory settings for various purposes such as sample storage, centrifugation, and mixing of small volumes of liquids.