A metered dose inhaler and in particular, a breath actuated metered dose inhaler, providing a valve port (1095) and a diaphragm (1000) for a pneumatic force holding unit of a breath actuated metered dose inhaler, a flap valve (36) for the canister fire system of a breath actuated metered dose inhaler, as well as methods for manufacturing and assembling the same. The valve port comprises an annular boss (1100) defining a valve orifice channel (78), wherein valve port further comprises two or more radially outwardly extending projections (1106,1107) defining a path through which polymer entered the boss during injection moulding, the projections being substantially uniformly circumferentially separated.
