A micro blood collection tube, also known as a microtainer or capillary blood collection tube, is a small-sized tube used to collect a small volume of blood for various diagnostic tests. These tubes are designed to collect blood through capillary action from a fingertip or heel stick rather than through venipuncture (drawing blood from a vein). They are typically made of plastic or glass and come with a variety of additives depending on the specific tests being performed. It features a capacity up to 0.25 mL.