The Flowmaster® Flow FX® Cat-Back Exhaust System is designed for 2020–2025 GM 2500HD and 3500HD trucks equipped with the 6.6-liter gas engine. Built from durable 409 stainless steel, this system features a 3.50-inch inlet transitioning into dual 3.00-inch mandrel-bent pipes for improved exhaust flow and long-term reliability. The Flow FX straight-through muffler delivers a deep, moderate performance tone while maximizing exhaust velocity.

Dyno testing shows gains of +9 horsepower and +10 lb-ft of torque at the rear wheels. This system exits out both sides behind the rear wheels and includes dual 4.50-inch black ceramic-coated stainless steel tips, adding a bold, custom appearance. Installation is simple with factory-style hangers, complete hardware, and detailed instructions included for an easy at-home installation.

Fitment

• Fits 2020–2025 Chevrolet Silverado 2500HD with 6.6L Gas
• Fits 2020–2025 Chevrolet Silverado 3500HD with 6.6L Gas
• Fits 2020–2025 GMC Sierra 2500HD with 6.6L Gas
• Fits 2020–2025 GMC Sierra 3500HD with 6.6L Gas
• Dual side exit configuration
• Uses factory hanger locations

Features

• Gains of up to 9 horsepower and 10 lb-ft of torque
• 3.50-inch to dual 3.00-inch mandrel-bent 409 stainless steel tubing
• Deep, aggressive-to-moderate tone from Flow FX straight-through muffler
• 4.50-inch black ceramic-coated exhaust tips
• Includes complete hardware and factory-style hangers
• Easy installation

Specifications

• Brand: Flowmaster
• Catalytic Converter Included: No
• Catalytic Converter Quantity: 0
• Category: Exhaust
• Clamping Type: Flat Band
• Clamps Included: Yes
• Exhaust Series: FlowFX
• Exhaust Tip Color: Black
• Exhaust Tip Connection: Clamp-On
• Exhaust Tip Cut: Angled
• Exhaust Tip Diameter: 4.50 in
• Exhaust Tip Edge: Rolled Edge
• Exhaust Tip Finish: Black Ceramic Coating
• Exhaust Tip Intercooled: No
• Exhaust Tip Length: 11.00 in
• Exhaust Tip Material: 304 Stainless Steel
• Exhaust Tip Quantity: 2
• Exhaust Tip Resonated: No
• Exhaust Tip Shape: Round
• Exhaust Tip Wall: Single Wall
• Exit Style: Dual Out Side
• Finish: Natural
• Gasket or Seal Included: No
• Grade Type: Performance
• Hangers Included: Yes
• Inlet Type: Flanged
• Main Piping Diameter: 3.00 in
• Mount Type: Uses Factory Hangers
• Mounting Bracket Included: No
• Muffler Body Height: 5.00 in
• Muffler Body Length: 18.00 in
• Muffler Body Material: 409 Stainless Steel
• Muffler Body Shape: Oval
• Muffler Body Width: 10.00 in
• Muffler Color: Silver
• Muffler Finish: Natural
• Muffler Flanged Inlet: No
• Muffler Flanged Outlet: No
• Muffler Included: Yes
• Muffler Inlet Connection: Slip-Fit
• Muffler Inlet Inside Diameter: 3.50 in
• Muffler Inlet Location: Center
• Muffler Inlet Outside Diameter: 3.63 in
• Muffler Outlet Connection: Slip-Fit
• Muffler Outlet Diameter: 3.00 in
• Muffler Outlet Location: Dual
• Muffler Outlet Quantity: 2
• Muffler Overall Length: 24.00 in
• Muffler Part Number: Kit Only
• Muffler Quantity: 1
• Muffler Series: FlowFX
• Muffler Type: Absorption
• Part Type: Exhaust System
• Pipe Color: Silver
• Pipe Material: 409 Stainless Steel
• Product Type: Exhaust System
• Sound Level: Moderate
• Spring Bolt Kit Included: No
• Sub Category: Exhaust and Tail Pipes
• Tail Pipe Outlet Outside Diameter: 3.00 in
• Tail Pipe Quantity: 2
• Tail Pipe Tapered Outlet: No
• Tip Logo: Embossed
• Type: Cat-Back
• Valve Included: No
• Valve Type: Not Applicable

This system is engineered to enhance sound, improve performance, and deliver a clean, custom look with a straightforward installation.