Ribbed Frender Bracket
The Frender
$30-35 USD 
This Bracket bolts to the underside of Butts seats and allows you to solidly mount the seat to a ribbed fender, allowing the seat to sit directly on the rib while better supporting the passenger.
Comes with hardware.
This will also fit the Backseat and Lazyboy perfectly.
Available in Nickel Plated and Raw and now Stainless!