When buying outdoor clothing or equipment, you may come across the term ‘Hydrostatic Head’. This term refers to how waterproof the fabric is.
If an outdoor jacket has a Hydrostatic Head (HH) measurement of 5000mm, this means the fabric can hold 5000mm of water in a column before it starts to leak.
Therefore the higher the value, the more water and water pressure the fabric can hold before the water comes through.
As a rule of thumb, a basic waterproof outdoor jacket has a 3000mm HH value. At this value the fabric is classed as waterproof.
Therefore, if you are looking for a jacket that is highly waterproof and will withstand heavier downpours and extreme conditions, a higher value HH is needed, such as a Hydrostatic Head value of 5000mm.
An example of a shooting jacket that has a HH value of 5000mm is the Highlander Rexmoor Camouflage jacket.