Black Diamond Tripod Bivy/Lightsabre Bivy Ground Cloth

Backcountry.com says:
The Black Diamond/Bibler Tripod Bivy/Lightsabre Groundcloth is, predictably enough, a fitted groundcloth to protect the bottom of your Lightsabre or Tripod Bivy. Reasoning that the designs of both Bivys are identical, and that different materials don't change the shape, BD and Bibler chose to utilize the same groundcloth for both. Tough enough to survive years of being spread over rocky, nasty terrain, the Groundcloth adds minimal weight but gives substantial protection to your beloved bivy.