Yes, my single stage dual guage regulator came from them in 2012, is on its 18th 2Kg fire extinguisher and works fine driving my drop checker to green approaching yellow no issues. Easily adjustable bubble rate as well.
Single stage regulators have a single pressure reducing stage that reduces the 55bar tank pressure down to say 3 bar (generally fixed) pressure. These are simpler and cheaper but suffer from loss of pressure when tank starts getting empty. The tank pressure stays at 55bar as the liquid CO2 evaporates, however once the liquid has all gone the tank pressure starts to drop. My regulator just starts loosing output pressure as tank pressure falls, easily seen by bubble counter bubble rate dropping and drop checker in tank no longer as green. My regulator eventually stops outputing at 15bar, but generally I have changed the tank by then. I usually get about a couple of days to a weeks notice as I can see the bubble rate is falling and have plenty of time to change the cylinder.
However some single stage regulators, especially the cheaper ones, aren't really a regulator (technically a flow control valve), consisting of a pin hole in metal plate or fine metal sponge reducing the flow (and pressure). They are fine until the tank pressure drops when can loose regulation and dump the remaining tank contents into the fish tank. This is end of tank dump. This is fine if it is a 20gr or 100gr disposible CO2 container, b*gger all gets dumped so makes no difference, but if the remains of a 2Kg fire extinguisher gets dumped this is a lot of gas and people have reported gassing all their fish.
In my experience the single stage CO2supermarket is fine, just loses bubble rate when tank starts losing pressure. Change tank and all is OK.
A dual stage regulator consists of two pressure reducing stages, one reduces tank pressure to say an intermediate pressure of 14bar and another regulator reduces the 14bar to an output pressure of say 3bar. These tend to have a variable output pressure control as well. These do not suffer from end of tank dump and keep providing constant output pressure as tank pressure falls. One problem is you get b*gger all notice the tank is empty (a day if lucky) if you are not watching the tank pressure, as the output will just stop once tank pressure is low enough and you can end up running lighting persiods with out CO2.
So take your choice. I would probable choose a dual stage regulator if I was buying again as I can see the regulator pressure guages when looking at the tank (and I weigh the FE every so often to work out how full), so running completely out of CO2 for me would probably never happen. Also gives another knob to fiddle (output pressure) along with needle valve to complicate CO2 injection rates and make things harder to get right as a downside.
