A type IV conformable pressure vessel has improved mechanical coupling between an outer composite shell and a boss. The pressure vessel comprises an inner polymeric liner having a flare edge fixedly coupled to the boss. The boss has a bore in fluid communication with an interior of the pressure vessel. In addition, the boss has a shank extending between the liner and the outer composite shell. The shank includes a plurality of spikes projecting radially away from the boss. The outer composite shell of resin and fiber surrounds an outer periphery of the liner and an outer periphery of the shank. The spikes are embedded into the outer composite shell to mechanically fasten the outer composite shell to the boss.