For 7mm skate axles. Each labyrinth seal fits into a groove cut into the inner race without touching the walls or bottom of the groove, so that dirt and water must go through a ?labyrinth? or ?U? shaped path to get to the inside of the bearing. The labyrinth seals are still removable for cleaning, but the skate time between cleanings is greatly increased. The Bones Bearing team of skaters who have tried these note that they are just as fast as ever, but are quieter, and stay clean longer. Bones Bearing factory testing confirms this.