These hubs are no-name formulas, laced to deep-v dp18. Cartridge bearing. Sealed. The outer face of the cartridges are exposed on either side of each hub. Despite the fact that I bought them with the information that they were sealed, I'm worried that the exposed face of the cartridge needs a dust cap to prevent the clearly visible seams (where the seal meets the metal) from being compromised.

Am I worrying for nothing? Is contamination kept out by the seal alone?