After months of dealing with my lousy regulator, I finally bought one of these. The difference is really something; MUCH finer and more stable control over CO2 flow, and thus reactor ph. I always had a feeling the "bubbes/min" thing was useless, because there's no such thing as a standard bubble size. The flowmeter reads in cc/min; my reactor is taking 2-3 cc/min. Not much, but because my bubble counter produces much smaller bubbles than most, it's more than a bubble/sec. Other reactors may be using more CO2 with lower bubble counts, and you'd bever know without a meter like this. I highly recommend it for anyone with a calcium reactor, its the RMA151SSV from dwyer instruments; about $40. Also, if you can use a cheaper regulator because you don't need the "precision" needle valve; just a steady output of 15-30lbs/in2.