A plunger, a syringe, and a method of making a plunger and a syringe are disclosed. The plunger includes a support ring and a cover disposed over and coupled to the support ring. A cavity defining a predetermined volume is defined between the support ring and the cover. The syringe includes a barrel defining an inner wall and the plunger inserted therein.本發明揭示一種推吸桿、一種注射筒及一種製造一推吸桿及一注射筒之方法。該推吸桿包含一支撐環及安置於該支撐環上方且耦合至該支撐環之一蓋。界定一預定容積之一腔經界定於該支撐環與該蓋之間。該注射筒包含界定一內壁之一筒體且該推吸桿插入於該筒體中。
