The Millennium M10 delivers medical grade oxygen up to 10 Liters Per Minute (LPM), providing a great oxygen therapy solution for patients who need higher oxygen flows than the 5LPM provided by most standard home concentrators. Millennium M10 has fewer parts than most other oxygen concentrators and is built for reliability so that it is easy to use and easy to own. Continuous Flow Oxygen Output The Millennium M10 features a twin head compressor that enables a higher airflow and greater oxygen concentration up to 10 Liters Per Minute (LPM) of medical grade oxygen. It is ideal for people with higher oxygen needs than those provided by most home oxygen concentrators. Durable, Safe & Reliable Designed to be largely maintenance free. The SMCT "sure cycle" valve was designed specifically for the Millennium; while protective tubing neatly guards the concentrators electronic protect against electric shock. Millennium M10 features durable construction with high grade caster wheels built to withstand rigorous usage 24-hours a day, 365-days a year. Oxygen Percentage Indicator (OPI) Millennium M10 is available with or without an Oxygen Percentage Indicator (OPI). If you upgrade to the Millennium M10 with OPI in your shopping cart your system will ultrasonically measure oxygen output for purity and uses audio and visual indicators to alert you to the current oxygen status and any drops in overall concentration levels. The OPI will display a GREEN light during normal operation (oxygen concentration levels greater than 82%),