Base Plate X-1 for Montgomery, Northwoods, Victor, and Duke 1 1/2 coils. Also Northwoods 1 3/4 and Bridger 1.65 coils. Base plates keep the traps frame from bowing when using strong springs or 4 coils. The plates are 3/16" thick with a centered D-ring for attaching swivels and chain. Instructions are included, welding is required.