These Van/RV/Camper/Boat Swivel Seat Bases are designed for Aftermarket seats with 8" x 11" Bolt Patterns on slide track to fit to the top pf these pedestals. The bottom Bolt Pattern 7.5" x 7.5" . These Swivel Van , RV Seat Bases can rotate 360 degrees. The pedestal will lock in the forward position. These are universal fit so will require drilling for most applications and you may need to create your own adapter plates. There are 4 heights of Pedestals available. 3" , 5.5" , 7" and 10"