The syringe piston, typically made of high-performance materials such as halogenated butyl rubber, is located inside the syringe barrel and achieves precise liquid control through push-pull operation. In pre-filled syringes, the piston must precisely fit with components such as the syringe barrel and plunger; in pen syringes, it must work in conjunction with the pen cartridge and mechanical device to ensure accurate drug delivery. The fit between the piston and the syringe barrel/pen cartridge must meet two core requirements: firstly, to construct a reliable seal to prevent drug leakage; and secondly, to maintain adequate slippage to ensure smooth injection. This precise fit directly affects the performance of the syringe and the accuracy of drug delivery.
