Ground cloths are useful for protecting an inflatable sleeping pad from sharp objects that might puncture it. Polycro is our favorite material because it is lightweight (4 oz. for a two-person size) and cheap. Gossamer Gear sells it for $10. However, we rarely use ground cloths because they can be substituted by smart campsite selection, backpacks, packrafts, dry bag style pack liners, or are unnecessary if you sleep on a closed cell foam pad.
Inserts have a waterproof floor and bug netting canopy. They provide the most comfort in very buggy places and are the best value option for protecting two people from insects. They are also the most comfortable option for hot nights or for curling up with someone else or with a book. Many different companies make model specific inserts. We recommend purchasing a two-person version and suspect that the Mountain Laurel Designs DuoMid and SuperMid Inserts could be the best for pyramid tarps. For A-frame and flat tarps the Hyperlite Mountain Gear Echo II Insert is the best we know of.
Bug bivis have a waterproof floor and bug netting that covers your sleeping bag. These are good for solo use in hot, buggy climates, but we find that inserts are more comfortable because they have more space and are a better value because two people can use them. An example is the Mountain Laurel Designs Bug Bivy.
Water Resistant Bivy Sacks
For solo use we prefer water resistant bivy sacks to bug bivys because they are a better value and much more versatile. We also prefer water resistant bivys to inserts for winter use because they block spindrift and are warmer. Unlike climber style bivy sacks, which are made entirely with waterproof fabrics, water resistant bivys have a waterproof floor and sides, water resistant top, and bug netting in the head area. They serve as a ground cloth, completely seal out flying and crawling insects, block wind, stop spindrift, and add between 5 to 10 degrees of warmth. All for only 7 oz.!!
What To Get?
Now that you have a better idea of the modular components you can purchase to complete your shelter system, check out our complete ultralight tent review. This review provides in depth advice and information about which ultralight tent or shelter will best meet your needs.