You get 8 machined wheel spacers measuring 6.56 mm in thickness that allow you to convert your Marwe 620's to hold our 100 mm and 105 mm wheels. Marwe OEM wheels with their wheel spacers have a width of 37.3 mm, so by using 2 of these on each side or our built wheel of 24.2 mm, you get a matching total width of 37.3 mm so you don't pinch or spread the forks. These spacers also work to put our wheels onto the Marwe 610a aluminum skate rollerskis. For converting the older composite Marwe 610's use our 4.55 mm conversion spacers. Doing the conversion is super easy. You just need two 10 mm wrenches to slide out your axle, then put one of these on each side of the wheel in-between the forks, put the axle back through and you're done, and saved a lot of money! You'll be happy with the longevity of our rubber as well!