Stainless Works Collector Adapter 3 Bolt O2 Bung 3-1/2" x 2-1/2"Made from 304 stainless steel for maximum corrosion resistance. The nicest collector adapters available! These are TIG welded for strength and durability. Come with 3 1 2" 3 bolt flange and a 2 1 2" OD outlet. An O2 bung is welded into the tubing, space approximately 2" from the inside edge of the flange. This collector adapter comes with a limited lifetime warranty and proudly made in the USA.