Belomo Triplet loupe - nice and sharp, crisp image. 15x is about perfect to see what you need with a bright image and not too much "judder" effect from the magnification. There is a 20x which can be useful too, but its image is dimmer. Much better than the plastic or single-element loupes, ugh.
Of course you can get more magnification (USB microscope), but for daily cleanings and general inspection that is unnecessary!