Radius Sub - 4.5" R-Box - 3.5" REG Box (Direct)..
The Broadest Selection. Period.
If you need sub, you are in the right place. At Radius, we offer more adaptors and crossover subs than anyone. We have hundreds of subs in stock, ready to go, right now. Or we can cut a custom sub for you quick.
Connection: 4.5" R-Box x 3.5" API REG Pipe Box
Hardness: 32-36 Rockwell C