Check your hub: double-wall hubs have more pronounced lines than single-wall ones.
If yours looks like the image on the left, choose single-wall.
If it matches the image on the right, choose double-wall.

Check the inside of your hub: double-wall hubs have more noticeable ridges than single-wall hubs.
If your hub looks like the image on the right, choose the single-wall option.
If it looks like the image on the left, choose the double-wall option.