For a long time Hi-Fi Tuning claimed there was no direction, but I always found there was, but it was predictable judging this from the printing on their fuses. With IsoCleans I have always found the arrow going with the hot side input is the best sounding, so I would confirm the current flow direction is the right direction for the arrow.
I should say also that when Synergistic Research tunnels fuses they do so in the direction of current flow. This greatly improves the sound as does painting the glass with AVM paint.
I should say also that when Synergistic Research tunnels fuses they do so in the direction of current flow. This greatly improves the sound as does painting the glass with AVM paint.