This high quality hood is imported from England, where some of the best rubber products are found. Three hoses provide ventilation, one in each nostril and one for the mouth. There is an inflatable bladder inside the hood that puts pressure on the head when inflated. To apply more pressure just keep pumping the rubber bulb. To release twist the valve above the bulb to release the air. This allows for a very snug fit and provides an interesting sensory deprivation effect. This is a one size fits all, the rubber is very durable and stretchable. Designed for a snug fit. Corn starch can be used to help glide the hood over the head. Note this not one of those cheap mass produced hoods.