Taiwan Yuasa has designed double layer lid with explosion proof stones, which can make water flows back, single point venting, and electrolyte anti-spilled.

SMF type has those features above, which has lower water-loss and better lifespan.i-spilled. 

Anti-spill

The unique Labyrinth lid design provides anti-spill protection

Reduce moisture loss

Special lid design ensures water flows safely back into the battery.

Single point venting

The gas which generated from re/discharging would lead to both side of battery by unique lid design.

Both sides of lid has explosion proof stones, which can restrict the path of flame or spark inside the battery that cause probable explosion to enhance safety.