Bearings should always have a spacer between them and a washer either side. Hangar-washer-bearing-spacer-bearing-washer-nut. No exceptions. That setup helps keep the whole wheel straight, reduces movement on the axle, and stops the bearings rubbing against things as they spin. That means your bearings stay smoother and run faster for longer; not using spacers and washers means you’re just going to need to buy new bearings sooner.
(…really, now we think about it, maybe we shouldn’t be telling you this. Hm.)
All trucks should come with enough washers for this setup, and some bearings (like the Tektons) have the washers built in. But if you need more – maybe you want to push the wheels further away from the hangar, or you’ve lost the ones your truck came with – these Speed Rings are what you want. There’s 8 washers in one pack – enough for one complete setup.