In reality, you will find that most professional M Class dust extractors will have similar suction rates and filtration levels. This means the applications they can be used for are fundamentally the same. The difference will come down to features on the machine. A true M Class dust extractor will have an audible alarm to advise you when the suction rate has dropped, for example a blocked hose or full dust bag. You will generally find that when working on site, the health and safety manager will insist on using M Class dust extraction.