The biggest trouble I always had with my swing-arm hydrometers were stupid little bubbles that always got caught on the arm. Sure, I can tap-tap-tap and stick a toothpick in there for stuborn ones... but it always ended up taking forever just to check the Sg
. And because of the hassle, i never trusted the results. Now with the refractometer, I take it out of the case, drop two drops of water on it, hold it up to the light, wipe it off and put it back in the case. It takes seconds and i'm 100% confident in the reading.