When used properly, the OPSAK Barrier Bag 12 x 20in - 2pk is 100% water and airtight. The bags are considered disposable and will need to be replaced after extended use. The body of the bag will far outlast the closure. The closure is a lighter-weight material in order to ensure pliability to create 100% contact throughout the closure. The body of the bag is a durable film that will far outlast the closure.