You just by those ones because they because the unisexual excellent performance is the best.
... but yeah I also use the rolls and cut them to size/shape as required.
The one that's been linked is a channel bag user only. I prefer one with a snorkel. Ended up buying one from misty gully. Works better than the previous one when sealing foil bags.
They have a smooth section up the centre that you can cut and reseal to
reduce the bag size. I don't know whether they are oxygen barrier but I can't
smell the hops through them, which is better than the Zip-Lock Bags I was using.