These bearings are good bearings but somewhat overpriced. They are filled with a thick gunky grease, but actually they broke in after just one hour of transition skating and the grease will be good at keeping out dirt and moisture. I think it will be a long time before they need cleaning. Once broken in, they are about as fast as my set of Fracture 5s, which came with spacers (and should have come with washers) and were cheaper. Bones China Reds cost about £20 but are much faster. I will next try Enuff Blacks, which seem to be the same thing but only £15-- if these turn out to be as good as Reds there will be little point in these Wych bearings. Get only if you want the low maintenance of the grease and don't need the extra speed of Bones.