Waterproof Poly Pack Liner
Waterproof Poly Pack liner bags are perfect for giving your pack an extra layer against water and moisture. Ultralight, completely waterproof and tougher than a garbage bag. Simply fold over the top to seal out moisture from above. You can patch them easily with packing tape.
Great for packs of any and all sizes (just cut it down to fit smaller packs).
Dimensions: 70 x 94 cm
I can't comment on the waterproofness as I did not get caught to a sufficient deluge but it did survive a 7 day hike with just a small hole which I suspect is from me stuffing something a bit too eagerly! The large size is a good fit for a 65l pack with plenty to spare.
It says in the description that you can patch them, but I can't see needing to do that for some time to come! Lightweight, super durable and the easiest way to keep your gear dry without having to stop and throw on a pack cover.