Syringes vary by the amount of insulin they hold and the size of the needle. They're made of plastic and should be discarded after one use.
An insulin syringe has three parts: a needle, a barrel, and a plunger.
* The needle is short and thin and covered with a fine layer of silicone to allow it to pass through the skin easily and reduce pain. A cap covers and protects the needle before it is used.
* The barrel is the long, thin chamber that holds the insulin. The barrel is marked with lines to measure the number of insulin units.
* The plunger is a long, thin rod that fits snugly inside the barrel of the syringe. It easily slides up and down to either draw the insulin into the barrel or push the insulin out of the barrel through the needle.
The plunger has a rubber seal at the lower end to prevent leakage. The rubber seal is matched with the line on the barrel to measure the correct amount of insulin.