A reservoir (402) for connection to a spray gun has a lid (410) provided with an outlet spout (415) that is rotatably received in a socket of an inlet adaptor (419) connectable to the spray gun. The lid (410) has a spring leg (425) spaced from the outlet spout (415) with a projection (426) at the distal end for self-latching engagement with a flange (423) of the adaptor (419) to secure releasably the reservoir (402) to the spray gun. The engagement of the projection (426) and flange (423) enables the reservoir (401) to be rotated through 360° to adjust the position of the reservoir (402) while attached to the spray gun.