For you gram wienies - yes, you! - the Gossamer Gear Polycryo Ground Cloth is the lightest ground cloth that we know of (1.3 oz / 36 g) that is tough enough for multiple trips. Half a space blanket is lighter, but one puncture and they rip apart. I've had the same Gossamer Gear Polycryo Ground Cloth out in the desert for 7 nights and the dunes for 5 nights without any damage.
I used the Polycryo Ground Cloth with a sleeping bag and with a quilt, without a bivy. Both bag and quilt sometimes migrated off the Ground Cloth and into the dirt. I'd like to see the Gossamer Gear Ground Cloth offered in a slightly wider version. Gossamer Gear offers a 6' x 8' ground cloth but in a heavier material (apparently wider Polycryo sheets are hard to find).
Destruction testing further confirms that the Gossamer Gear Polycryo Ground Cloth is tough and puncture resistant as claimed. I cut a couple of pieces from my used Ground Cloth and destroyed them. I ground a piece under my foot on concrete a few times - no holes. When I next ground it on tiny gravel, I produced several holes. When I pulled the edges of the Polycryo square, it did not tear immediately (unlike a space blanket).
I poked a sharp stick into the second square of Polycryo until it pierced the material. It took a little, but impressive, bit of push to force the stick to puncture the Polycryo. I pulled on the edges of the square and, not weakened by the grinding on concrete test, it took some extra effort to stretch the hole until the Polycryo tore.
Features and Specifications
Tough and puncture resistant
Multilayer, cross-linked polyolefin film
Tensile strength of 15,400 p.s.i. per ASTM D-883
0.55 oz/yd2 (19 g/m2)
32" x 96" (81 cm x 244 cm)
1.3 oz (36 g)
MSRP $3.95 for two
Available in heavier material (0.9 oz/yd2 / 31 g/m2) in a larger size (6' x 8' / 1.8 m x 2.4 m)
"Gossamer Gear Polycryo Ground Cloth SPOTLITE REVIEW," by Carol Crooker. BackpackingLight.com (ISSN 1537-0364). http://backpackinglight.com/cgi-bin/backpackinglight/gossamer_gear_polycryo_ground_cloth_spotlite_review.html, 2005-07-07 03:00:00-06.