A syringe is provided. The syringe includes a syringe cylinder, a needle assembly and a push rod. The syringe cylinder includes a contraction section which is located at an end of the syringe cylinder. The syringe cylinder defines an accommodating space. The needle assembly includes an adapter, a needle and a needle base. The adapter is arranged in the contraction section detachably. The needle base is assembled to the adapter. The needle is disposed on an end of the needle base remote from the adapter. A code is formed on an outer wall of the adapter. The code is engraved by a mold which molds and manufactures the adapter, and the code is a height-differentiated structure. The push rod includes a resilient piston and a push member. The resilient piston is slidably arranged in an interior of the syringe cylinder. An end of the push member is disposed through the resilient piston.本發明關於一種注射器,其包括一注射筒、一針具組及一推桿。該注射筒包括一位於該注射筒一端之收束段,該注射筒圍構一容室。該針具組包括一轉接頭、一針基及一針頭,該轉接頭可脫離地設於該收束段中,該針基組接於該轉接頭,該針頭設於該針基遠離該轉接頭之一端,該轉接頭之外壁設有一編碼,該編碼係由製造成形出該轉接頭之模具所刻印之凹凸結構。該推桿包括一彈性活塞及一推頂件,該彈性活塞可滑移地設於該注射筒內部,該推頂件之一端穿設於該彈性活塞。1‧‧‧注射器2‧‧‧注射筒3‧‧‧針具組4‧‧‧推桿21‧‧‧收束段22‧‧‧容室211‧‧‧第二凹槽31‧‧‧轉接頭32‧‧‧針基33‧‧‧針頭34‧‧‧編碼35‧‧‧密封環件36‧‧‧凸柱312‧‧‧直筒段313‧‧‧斜錐段314‧‧‧第一凹環315‧‧‧內螺紋段321‧‧‧外螺紋段41‧‧‧彈性活塞42‧‧‧推頂件43‧‧‧卡扣部411‧‧‧凸垣412‧‧‧凸部
