Conversation so far:
What Wu-Tang Clan's The W?
The W is the third studio album by American hip hop group Wu-Tang Clan.
Was Wu-Tand Clan's The W a success?
The W was released in November 2000, and was mostly well received by critics, particularly for RZA's production.
Did Wu-Tang Clan's The W win any awards?
The album was certified platinum by the Recording Industry Association of America (RIAA).
What is Wu-Tang Clan's Iron Flag?
In 2001, Wu-Tang Clan released Iron Flag, an album which made extensive use of outside producers and guests.

Question: Who did they collaborate with?
Self-contained rewrite: Who did Wu-Tang Clan collaborate with on Iron Flag?