Scienceware^® flow indicator 

Gives immediate visual indication of cooling-water (or gas) flow by rotation of white ball in the circular channel. A minimum water flow of 50 mL/min (indicator in horizontal position) or 140 mL/min (indicator in vertical position) will actuate the ball. With air, the corresponding minimum flow rates are 3 and 8 L/min. Maximum pressure is 50 psig with water and 10 psig with air.

Scienceware is a registered trademark of Bel-Art Products.