If you have hardwood floors then this air pump is an absolute godsend, but I get ahead of myself. First of all, it's cheap. I picked up a single unit for 20 australian dollars full price and that comes with a years warranty, a very good deal. Secondly, it actually looks quite good! Where as most units (the ones I've been through at least) look like plastic, humming bricks this unit looks sleeker, glossier and generally easier on the eye. Here's a picture, my apologies for the poor quality of the camera phone. Thirdly, it is very adjustable. It has a dial system with 4or 5 intensity settings, including a high setting that actually is high and a low setting which actually is low. You can also buy units with multiple air hose outlets, each with an individual dial, so it's great if you want to have, say, a bubbling diver and an air curtain going from the same device but still have them going at different intensity levels. Finally, and most importantly, it is completely and utterly silent. Really, even on a hard wood floor. The unit has special legs, designed to function a lot like joystick controllers, which allow the unit to vibrate without making noise. The only way you can hear the motor is if you press your ear against it, or if you place objects or power cords on top of it. But you shouldn't do that anyway. All in all it is a very good pump! One odd thing, however, is that the pump comes packaged with a strange plastic shape and some screws in a zip lock bag, but neither the box, the instructions of the items themselves give any clue as to what they are and what you're supposed to do with them. I think they're trying to make me paranoid.