100% waterproof pouches

I got a Seat to Summit Stopper Dry Bag which has worked in a short gorge hike. But next month I'll be doing a far more serious hike: Bookookoorara Ck that will put the dry bag under a real test. To make sure my camera and phone won't get damaged by a possible water leak I need a waterproof pouch as a second layer of protection.
I found this on eBay:
Link
Are they good enough?
Cheers!
I found this on eBay:
Link
Are they good enough?
Cheers!