Hypodermic syringes are used with hypodermic needles to inject liquids or gases into body tissues, or to remove from the body. Syringes for insulin users are designed for standard U-100 insulin in the United States. The dilution of insulin is such that 1ml of insulin fluid has 100 standard "units" of insulin. Since insulin vials are typically 10ml, each vial has 1000 units. Outside of the United States, there are other dilutions available such as U-40, or 40 units of insulin per 1ml of solution, so syringes specifically for this strength should be used with this kind of insulin.