Tents
Rain resistance is measured as a hydrostatic head in millimetres (mm). This indicates the pressure of water needed to penetrate a fabric. Expectant or wind-driven rain has a higher pressure than light rain. Existing on a groundsheet increases the pressure on any baptize underneath. Fabric with a hydrostatic head of 1000 mm or less is best regarded as shower resistant, with 1500 mm being as usual suitable for heat camping. Tents for year-round appliance generally have at least 2000 mm; expedition tents intended for extreme conditions are often rated at 3000 mm. Where quoted, groundsheets may be 5000 mm or more.
There are three indispensable configurations of tents, each of which may appear with alive with http://www.tentsforsale.org variations: