The Tropf-Blumat Maxi acts as a regulator and dripper, just like the standard Tropf-Blumat. This one is 9 inches long though. You put it in the ground 6 - 7.5 inches so it senses the moisture at a deeper level. This is important when your plants get bigger because the regular Blumat sensor might turn the water off too soon. And this one might turn it off too soon if your plant still has surface roots. Some growers use both - especially if they are growing in coco or a hydroponic system.
Note: Blumat Classics (Juniors) and bottle adapters are designed for houseplants while Tropf-Blumat Sensors (the one's with the small adjustable brown knob on top) are designed for greenhouses, growrooms, decks, and outside gardens. Blumats Austria says "Please don't use the Tropf-Blumats indoors" because if hooked up to a constant water source and a pet, guest, or user-error somehow causes a run-away, it could damage an indoor floor, drywall, carpet, or furniture. We, and many others, do in fact use these systems inside ourselves, however, we are generally around enough that if a problem did occur, we would be able to notice a problem and fix it in time (not the case if someone is on vacation). We have many guides for being able to set these up the proper way and avoid a run-away or general mistakes. Please contact us for any help, we are always here to help make your life easier.