Dayton RSS210HO-4 Subwoofers in custom MDF enclosures. They are designed similar to the JL Audio 8w7 Stealthbox but even smaller. They go up against the back wall and dont extend past the steel seat brackets. They are constructed from 3/4" MDF, CNC cut, glued and screwed. They have 3/4" Bracing inside as well. Very strong build. They could moonlight as truck ramps.. You can fit a pair of them u...