These Small Block Chevy Aluminum Adapter Plate Kits allow you to use a larger tube size to maximize power. The Standard Chevy bolt pattern will only allow you to use a 1-3/4” (44.5mm) tube size before interfering with the bolt holes. Featuring 9/16” (14.5mm) thick machined 6061 T-6 aluminum with steel threaded inserts for the header bolts, these are the ultimate way to increase the capability of your engine. Each kit comes with all hardware to install the plates.