I received my groundsheet as a birthday present, in winter, and took it on a number of walks, where its small packed size of 21.5x8x11cm (8.5"x 3.25"x 4") and light weight 295g (10.4 oz) made it an inconsequential daypack or cargo pocket addition.
Made from a tough Ripstop nylon construction, dual-coated with 3000mm Silicone and PU, it is fully seam-sealed with heat tape to be both 100% waterproof and puncture resistant. When staked out the Bathtub Groundsheet measures : 210x90x15cm (6'11"x2'11" x 6"), plenty big enough to fit me, and my gear, and the bathtub wall height is plenty big enough to keep my bedding in, or incidental wet out.
The corners are heavily reinforced and tailored to stand upright without stressing the seams and feature tape reinforcement to hold upright without sagging. This is bolstered further by built-in metal posts in the corners to hold it up, as well as sewn in buttressing peg-out loops extending outwards. the top edge of the corners also feature a loop sewn in to fit fly poles if used, and sewn in snap-points allow the groundsheet to marry up with the compatible Ultralight Ground Bug Net to create a fully-enclosed sleep system by pairing with this groundsheet. Nice forethought.
The included 4 Y cross-sectioned 7001 aluminium pegs have retention notches and a built in pull-cord for ease of removal.
When fully staked out and pulled taught, the bathtub effect is very stable, and provides a good barrier against the outside. the ripstop nylon is smooth and whilst not breathable, very comfortable to lay on directly, even after being in full sun.
I liked that it was big enough for me to fully stretch out on, as i'm quite tall. i'd want a tarp strung up over it to sleep on, just to give some cover, and I suspect leaving the most down-hill corner flat to allow any water a drain-off spot might be prudent without one.
I've woken up in a pool of water once whilst camping and don't recommend it.
The whole system comes with own drawstring bag for ease of carry and is small and light enough to be stuffed in a cargo pocket. I have been keeping it in my car along with some light picnic hiking gear and have used it as a picnic blanket a number of times. I think i'll be picking up the bug net and one of the Alton goods tarps to complete the set, and will test it out for sure.