|Mike uses Fender|
Mike Dirnt's bass rigs, cabinets, and sounds are impressive here. You'll find that he doesn't use a lot of effects, in fact, he uses NONE. He plays straightforward precision bass guitar, and uses Fender's only.
Fender custom makes the Mike Dirnt guitar and it's a precision bass, much like the standard punk option. It's not "down tuned" or anything special outside of being a signature sound and style that the band is known for. As I posted yesterday in my update about the song "Warning", the band has some unique bass lines and provides an interesting look into punk and pop bass guitar work.
This video shows off the rigs they are using. If you want to buy a Mike Dirn't signature bass guitar from Fender, you can do so by clicking here, and see what he uses live in the video clip below, around mid-way through the whole thing.