HyVent is a waterproof and breathable fabric with a PU (polyurethane) coating that consists of a multilayer formula for waterproof protection, moisture permeability and durability. ** In excellent used condition. ** How does it work? The North Face Hyvent works by providing a completely waterproof shell that protects in rain and snow conditions. The North Face Hyvent is also designed to be highly breathable, so it won't smother you with heat despite its barrier-like properties. Best of all, The North Face Hyvent is built to last with a highly durable construction.