The insulin syringe is basically not different from other kinds of syringes. It has the same essential parts as the others, but it is designed with a slimmer barrel and smaller needle.
Its task is to deliver insulin into the patient or recipient's subcutaneous (immediately below the skin) tissue. Since the amount of insulin injected is not that big, the syringe is designed to have a narrower and slimmer barrel. Since the injection area is subcutaneous, the needle is intended to be smaller, shorter, and finer than others.