LA Choppers Universal Exhaust Baffle (2.5" x 24) Great for motorcycle muffler / exhaust projects. Perforated tubing material is 22-gauge, grade 409 semi-magnetic stainless steel tube. 409 stainless is an excellent choice for exhaust systems due to its corrosion resistance. 1/8" diameter holes on 3/16" staggered centers. 33 holes per square inch.