The Official Online RBS 6 Nations Store is open. The store has everything you need to get behind your team during the RBS 6 Nations, plus the store is now fully stocked with a much wider range of rugby merchandise.
Williams has named a squad of 25 and is due to unveil his line-up closer to the game.
Williams admitted he was disappointed about the way Ulster fell 16-9 to the Scarlets in their opening league game.
"We know we missed tackles we should not have, although our second half performance was better," he said.