Badjas grondzeil

The bathtub shape hugs the floor better than any flat tarp I've tried, so there's zero gap where moisture can sneak in. Took it on a muddy weekend trip and the tent floor stayed bone dry, plus it folds down small enough to not add bulk.

Set it up under my tent in the rain last weekend and the bathtub walls kept the puddles from seeping in, which saved my sleeping bag from a damp disaster. It fits snugly under the footprint too, so no bunching or sliding around when I'm tossing and turning at night.

The bathtub design really does keep water out—after a rainy night, the floor of my tent was bone dry while the groundsheet had puddles on top of it. It's a perfect fit for my tent footprint and lays flat without any fuss.