Originally Posted by Dave Mayer

Holes are for grease injection. Slide the cover to the side and pump the hub with grease until the old contaminated stuff shoots out both sides. Hubs are now good as overhauled.

Anticipating the concerns of fussy and pedantic C&V individuals here, I will respond in advance that yes, the extra grease in the hub shell will add 0.2 Watts of extra resistance, until the surplus oozes out over time.

And yes, purging with grease will not clean out 100% of the old. The horror. Maybe only 95% clean. Repeat the purge and now only 5% of 5% remains. Clean enough now?

The old Campagnolo Record freewheel hubs were the best wet weather hubs ever made. No seals. But since it only takes a few minutes to clean out the internals of these by grease injection, they could last forever. These are the hubs I used on my rain bike.