The needle of A 1 is 0.45mm, which is suitable for children under 12. Because children's blood vessels are small and inconspicuous, they use the smallest needle infusion set A 1. The needle of A3 is 0.55mm, which is suitable for people over 12 years old. These people's blood vessels are stronger than those of children. A3 infusion sets with a needle size of 0.55mm are the most suitable.
Disposable infusion set is a common medical consumable. After aseptic treatment, a channel is established between the vein and the liquid medicine for intravenous infusion. Generally, it consists of eight parts: intravenous needle or injection needle, needle cap, infusion hose, liquid medicine filter, flow regulator, drip pot, bottle stopper puncture device and air filter. Some infusion sets also have injection parts and drug feeding ports.