Costas,
Please understand I have a very limited knowledge of brand names amongst vacuum sealers – given that here are some pictures which should help you understand the nature of channel bag material. This is a Food Saver bag – notice how this side of it is clear and smooth.
The other side has a bumpy texture to it so that air can be sucked out without causing the bag to collapse on to itself.
These type of bags are unlike the Drybag material which is smooth on both sides.
As for fat being needed for aging that’s a bit misleading. I think a better way of explaining is that marbled fat makes the aged meat taste richer. Surface fat will be trimmed off to personal taste, but benefits the aging effort, by meaning there is no or at least less trimming loss of the red meat. Another way to think of it is a fillet or a tenderloin has little or no fat and is already tender – aging will condense the flavor but when many people trim back to red meat there is too much loss.
Ron