I'm comfortable and roomy in a 6
But they threw me in the mix with all these gloomy lunatics
Who walk around depressed and smoke a pound of cess a day

from Eminem – Rock Bottom Lyrics on Rap Genius

A 6 is anything in the 600 series Mercedes, which is a luxury sedan as is referred to in the last line. The gloomy lunatics are just the lunatics and burnouts he lives around in Detroit.

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