Wikipedia :)
Rain resistance is measured as a hydrostatic head in millimetres (mm). This 
indicates the pressure of water needed to penetrate a fabric. Heavy or 
wind-driven rain has a higher pressure than light rain. Standing on a 
groundsheet increases the pressure on any water underneath. Fabric with a 
hydrostatic head rating of 1000 mm or less is best regarded as shower 
resistant, with 1500 mm being usually suitable for summer camping. Tents for 
year-round use generally have at least 2000 mm; expedition tents intended 
for extreme conditions are often rated at 3000 mm. Where quoted, 
groundsheets may be rated for 5000 mm or more.


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Tadas (TJ)
Aktyviam laisvalaikiui ir kelionėms
www.montane.lt / www.montane.co.uk
www.robens.de
8-620-10880 / tadas@tj-sports. com
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"0.5 B" <gadamynas@gmail.com> wrote in message 
news:hvf3es$4nu$1@trimpas.omnitel.net...
>o kaip tuos mm suprast - tipo, ant ištiesto audinio tokio storio vandens 
>sluoksnį išlaiko nepravarvant?  :)



>
> "TJ (T@diz)" <tadas@tj-sports. Kom> wrote in message 
> news:hvdknv$sb5$1@trimpas.omnitel.net...
>> Dar ziuret i firma reikia. Pvz MSR 1000 mm pasitikeciau daugiau nei 
>> Campus
>> 5000 ar 10'000. Cekais labiau pasitikeciau nei lenkais.
>>
>> O siaip turiu Easy Camp su 1500 mm - laiko jau 5 metai ir i vidu niekas
>> nevarva, nors buvo liuciu neblogu. Turiu Robens su 5000 mm - laiko treti
>> metai. Ko neimciau tai vieno sluoksnio palapines - ryte kondensatas 
>> stipriai
>> lases nuo lubu