Are you riding around with broken or missing spacers? If so, you need to take care of that. Your bearings take a lot of sidewall pressure and that impedes their ability to roll freely. Your weight isn't supported as well when they are missing or damaged and that has a big effect on your speed and possibily even your safety. These are your basic nylon spacers---nothing too fancy, but they get the job done and are surprisingly tough. 8 is what you need for a set of 4-wheels in-line skates. These fit in virtually all brands of skates with standard 608 size bearings. Rollerblade, K2, Bauer, Mission, CCM, Roller Derby, Roces, Oxygen, Tour and most other brands. There are some exceptions, but almost 99.5% of all skates can use these. They are designed for standard size bearings (not micro bearings). All skates have a chassis that is a standard size and width and this is the correct size no matter what size wheels you have. These measure about 15/16 across or 23mm (They should be identical to the ones you already have--just a different material). The interior diameter of the hole where the axle goes through is 1/4 or 7mm. There are a few exceptions--if your axles are wider than this they will not fit, but there are not a whole lot of skates out there that have axles like that.