3157 Flush mount Betts kit.
Machined aluminum bases-Polished
*WIDE BASE*  is 3.5" OD 
*NARROW BASE* is 3.1875" OD
Both designs will mount up in place of standard watermelons
Requires 2" center hole for 3157 plug.
Requires two 3/16 holes drilled horizontal on 3" centers.
*Bulb not included
Sold as each.