Abstract: A syringe assembly having a hollow barrel and a needle in communication with the barrel for receipt or discharge of material therethrough. A plunger is received within the hollow barrel. A cap member receives at least a portion of the barrel and locking members are provided for securing the barrel and cap in a number of relative axial positions. A frangible end closure may be provided on the end of the cap closest to the needle. The locking members permit different locked positions for exposing different amounts of the needle. The locking members may be formed on the barrel and cap and may consist of a series of formations on the barrel adapted to engage a series of formations on the cap. Ready locking and unlocking is permitted.