Down material is the light, fluffy coating clustered beneath the feathers of waterfowl that helps to protect them and keep them warm through natural insulation. Down insulation is made from goose or duck plumage, which is the soft undercoat of birds. Down insulates by trapping air and is prized for being light, easy to compress, long-lasting, and breathable. It is the insulation of choice in cold, dry conditions, or whenever reducing weight and saving space are top priorities. Down is warm, lightweight, and packable, and if well cared for, it retains its loft up. However, down is not super breathable and loses its loft when wet, which means it no longer is able to keep you warm. Proprietary technologies have been developed over the years to treat down at a microscopic level with a water-resistant application. This treatment allows down to resist light moisture without compromising loft. However, if submerged in water or exposed to heavy rain, even treated down will get wet, so it is essential to keep down-filled items dry.