There are about 2 1/2 inches behind the seat when it the seat is "up" and about 4 inches when the seat if folded down. Amps would be fine, but a sub would be tough.

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2007 Tundra 5.7, Double Cab, SR5, Blue Streak

TRD (stickers removed), de-badged, Volant Intake, Zoomers exhaust , Doug Thorley headers, Leer 100R, Bedrug, Curt front mounted hitch, Sirius interface kit, Tekonsha Prodigy brake controller, OEM alarm activation, Wet Okole seat covers, Stubby Antenna, Folding Rear Seat Mod for Double Cab, Unichip