For the backs, they come factory spec with 4" speakers.

You can modify it to fit both 5.25" and 6/6.5", however, it is a fiddily job.

I just installed 5.25" back speakers on my mates 06 wagon...it was a cnunt of a job :/ electric windows kept hitting the magnets and required some makeshift "spacers" and they were too wide, so the back door panel wouldn't go back on :/

took us a while but we managed, just get the spacers required for your speakers and you wont have a problem. see JBHIFI for spacers....

Good Luck

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2005 WRX STI