Spacers and speed rings are different parts. A spacer fits between the two bearings inside a wheel. Speed rings, sometimes called washers, sit between a bearing and the truck hardware. The product contents and exact arrangement can vary, so check the instructions for your setup.
Why alignment matters
When the wheel is assembled, its bearings should sit squarely in their seats. Misaligned parts or excessive axle-nut pressure can make a wheel bind. A spacer can support the bearing pair when the axle nut is tightened, but the correct fit and assembly still matter.
Check the parts before riding
Lay out the parts before assembly and identify which pieces belong inside the wheel and which sit outside it. Tighten the axle nut carefully, then check that the wheel rotates freely and does not move excessively from side to side. Do not leave a dangerously loose nut to compensate for a binding wheel; inspect the assembly instead.
DSCO set contents differ. Check the product page for whether spacers or washers are included, and read the installation guide if you are unsure about the order.