1. Generally, it is 5ml, that is, 5ml, which is often referred to as 5CC, but because the needle tube is thick and thin, the same 5 cm, the big needle tube for intravenous injection and the small needle tube for skin test are very different; 2. Therefore, you need to measure the radius of the needle tube, and then calculate it yourself: Cylinder volume = bottom area x height, bottom area = radius x radius x 3.14, height is 50 mm;