Initially the Solo he/o2 came with just the basic flow limiter, which is probably adequate for the Solo o2 unit, but with the helium sensor unit (mine) the flow rate has to be very precise, between .2 and .4 L/min. When trying to test a EAN tank with 27.5% and flow outside that required range, the helium sensor sampling showed some very odd MOD screens and warnings. Works well only when in the specific flow rate range.
I just got the BC inflator limiter and hose which will work fine when a 1st stage is connected to each tank. However, that requires moving the 1st stage among tanks or having a BC hose on each 1st stage... yada yada yada.
Hoping to pick up the pro flow limiter to give a bit more flexibility and accuracy into testing multiple tanks, while reducing the amount of wasted gases (ie: expensive helium).