PURPOSE: To facilitate the mounting and removal of a unit without requiring a bracket, equipment or tool by forming an opening part on a panel to which a flowmeter assembly or unit is related, and mounting the whole body by snap fitting.

CONSTITUTION: End caps 22, 24 are designed so as to have side flanges 44, 46 as means separated from the related end caps to mount a flowmeter assembly or unit 20 on a specified panel 12 by snap fitting. The side flanges 44, 46 have a form working so as to help the guide of the flowmeter assembly or unit 20 assembled on the panel openings formed on the panel in mounting, and the assembled flowmeter assembly or unit 20 is fitted to the front side 13A of the panel 12 from the front or front side. Edges 48 provided on the side flanges 44, 46 are engaged with the opening edges of the panel as ratchets.