You need to grease these bearings before use.

This kit is great for a first timer, it gives all you need, but the spacer for wide wheels. These bearings require manual greasing, as they are bone dry. I used ptfe grease to keep longevity and their smooth as glass feel. Also they use a plastic bearing race. I use German bearings with metal bearing races. So I was careful to grease with the best I could find to make these bearings last longer.