The Aerator is used to oxygenate the water / nutrient solution. The air tube has to be inserted on the top protrusion and can be made leak proof using the 3Dponics Air Lock. Coins are inserted into the slots provided so that the Aerator can rest at the bottom of the nutrient container, immersed in the water / nutrient solution. Know how to make this part better? Have ideas for new parts? Visit our website (https://www.3dponics.com) and join our Google+ community (https://plus.google.com/u/0/communities/111638904033818784260) to take 3Dponics to the next level! Ready to print this part? Compare 3D-printing prices across today's top service providers and get the lowest price for your 3D-printing project. Get your quote now at https://www.3Dprintler.com. "3D Printing Settings: -Low quality; 0.2 mm; 2 shells; 10% infill Tested on MakerBot, Ultimaker, M3D Micro and Formlabs"