These Level 1 pants were designed by the US military to help soldiers survive through any weather condition they encounter. As the first level in the 7 level layering system, they are worn against the skin. Because of the special durable construction of the fabric it not only provides insulation, it aides in the transfer of moisture (known as moisture wicking), all without the bulk.
These drawers are very durable and do not restrict movement. So go ahead and take that camping trip with confidence, just make sure to take along your ECWS Level 1 silk weight thermal pants.