I would rather have velcro than a zipper. I wonder how good it will open/close after some salt water diving?
I have a pair of these on both left and right side of my latest TLS350. I've got about 80 salt water dives on them over the past 6 months ... so far no problems with the pockets (wish I could say the same for the TLS350 )
To be clear, velcro is still used to secure the flap to the main bellow pocket. A feature of these pockets, is that the flap itself contains a medium sized pocket compartment mounted on the outside. It contains a couple of thin bungee loops and is big enough to easily hold a couple spare spools ... but mostly handy for isolating smaller items from the rest of the main pocket contents. The only thing I put in them currently are spare double enders (left side).
The zipper pulls for these outer flap compartments are on the smaller side ... which could a be an issue for some who dive with dry gloves.