The EU 0.2 mL tube with optical flat cap is a type of laboratory sample container. It is a small, clear tube with a flat-topped cap that has a flat surface, designed to hold a volume of 0.2 milliliters (ml). The optical flat cap provides a flat surface for optical scans and measurements, such as in spectrophotometry or fluorimetry experiments, which require a clear and flat surface for the measurement of light intensity.

The tube is commonly used in molecular biology and biochemistry applications, where small sample volumes are needed. They are also commonly used in sample storage and transport.