We measure a fabric's resistance to a water column, in mm (based on the ISO 811 standard). The higher the water pressure resistance, the more waterproof the fabric. Components 2000 mm waterproofing, resists up to 2000 mm of water pressure (which is roughly equivalent to a rain shower lasting 2 hours).
With waterproofing greater than 10,000 mm, the Alpinism Light jacket therefore offers a very high level of waterproofing.