So my truck came with the MTX Thunderforms speaker box under the rear seat. To me the sound was always a 4/10. Better than nothing but still really really sub par. A buddy of mine needed money and I bought his Rockford Fosgate P3 10" subs from him. They are huge compared to the MTX subs. They are both 10" but I swear the RF is more like an 11" sub. Its way wider. At least the mounting ring is at least 1" wider. To get them to fit I had to create some space. I made a ring out of 3/4" wood. The weird thing is that the opening in the sub box isn't perfectly round. Not even close. So I had to make this weird oval type shape. I also had to trim the mountings for the subs a little bit. I also have to raise the rear seats at least 3/4" to clear the box. Easy with some 1" round stock I had laying around. Fun little project. I hope they sound good! I don't know if this was typical but I used some black RTV silicone on the underside of the wooden ring. The mounting surface is a little uneven and I was worried that the screws alone wouldn't make a tight seal. Had some spare speaker box carpet from a project like 8 years ago. I am glad I don't get rid of anything. Look at the difference! Also, this music station or whatever on youtube is excellent.