Please note that the user capacity listed for each model is based on typical combinations of high-volume evacuators (HVE), saliva ejectors (SE) and nitrous oxide (N2O) scavengers that can work simultaneously in a conventional dental office setting. Typically, each HVE equals 1 user, each SE Equals 1/2 user, and each N2O scavenger equals 1/2 user. User satisfaction is a subjective matter. Ratings are shown for planning purposes only. Piping length and configuration can affect vacuum performance. For specific application, contact Midmark Technical Service for vacuum sizing recommendations.