They ARE NOT water proof.
They ARE NOT air tight.
They DO NOT HAVE “bomber” construction.
SO WHY are they essential when trying to add performance to a layering system?
With the addition of a 2 to 5 ounce / 50 to 150 gram wind shell you can easily expand the comfort range of your clothing in high winds, cool temperatures, and light precipitation. An ultra light wind shell layer excels when counted on to prevent conductive heat loss by shielding you from chilly gusts and light precipitation. It also offers a measure of shelter from sun and pesky insects in warmer surroundings. Additionally, by utilizing air permeable fabrics wind gear can offer a small amount of “breathability” to assist in bleeding excess heat. Finally, by being simple in construction and on the fragile side the highly compressible garment fits in the palm of your hand, making it easy to include in your trail kit and ideal for most activities.