Empi 3737 Spark Arrestor. Many Off-road Areas Require Some Form Of A Spark Arrestor To Limit The Chance Of Fires. Comes With Long Enough Screws For Additional Disc If Needed. Specs: Stainless Steel Body Disc Diameter 4" Length 11" Includes Mounting Bracket Clamp On Style Opening Diameter 2" Note: Can Be Welded On If Desired Spark Arrestor Discs Are Stackable Allowing Fine Tuning On Your Exhaust Flow For Maximum Horse Power And Torque. Removing Disc Will Increase Back Pressure, Adding Disc Will Reduce Back Pressure And Increase Flow And Noise.