PROBLEM TO BE SOLVED: To provide an elastic cap detachably attached to a cylinder tip portion of an outer cylinder in which a puncture needle projects from the cylinder tip portion, and an assembly for a syringe equipped with the same.SOLUTION: An elastic cap (18) of an assembly (10) for a syringe includes: a first inner diameter portion (44) having a smaller diameter than an outer diameter (c) of an annular head portion (22) of a cylinder tip portion (16) a stopper portion (48) provided at a tip end of the first inner diameter portion a second inner diameter portion (42) which is formed from the stopper portion to a bottom portion and has a smaller diameter than the first inner diameter portion and a bottom wall (36) provided at a tip end of the second inner diameter portion. The elastic cap has a housing hole (20) the minimum diameter (e) of which is 2 to 10 times of an outer diameter of a puncture needle (12), in which the stopper portion abuts on a tip end surface (22A) of the annular head portion and thus, a final insertion position of the cylinder tip portion is regulated, and which encapsulates a tip end of a needle hole (32) by insertion of a tip end of the puncture needle into the bottom wall.SELECTED DRAWING: Figure 1
