Reverse osmosis and ultrafiltration, commonly referred to as RO and UF, use membrane technology. The reverse osmosis system uses a semipermeable membrane that separates 99.99% of inorganic dissolved material from the water molecule. The ultrafiltration system uses a hollow fibre membrane to stop solid debris and microscopic contaminants. UF is a mechanical filter, but it can filter water down to the superfine level of 0.01 micron, hence the name ultrafiltration. Ultrafiltration is a filter system, while reverse osmosis is a process where molecules are separated.