I think they are electric. The back of the gauge only has 2 wires, and no vacuum nipple. I think it's specific only to S15's too. You can use the holder in S14's though, but you have to cut the top bit of the plastic to fit.
CONGRATS to Alvin(TOM's) for the achievement he had yesterday atGRA round 4.
He managed to secure 1st Runner-up for Open-PRO class OD in his yellow SW20.
Also congrats to Ashlyn for securing Fastest Female...