Remark RK-C1076S-01 R1-Spec Single-Exit Cat-Back Exhaust SS for 15-21 WRX/STI

Vehicle Fitment

• 2015-2021 Subaru WRX (VA Chassis; EJ255 / FA20DIT; Sedan; All Trims)
• 2015-2021 Subaru WRX STI (VA Chassis; EJ257; Sedan; All Trims)

Fitment Notes

• This is a full cat-back exhaust system, covering from the downpipe/J-pipe flange rearward through the midpipe, muffler, and single exit tip. It replaces the factory dual-exit rear exhaust configuration with a single center-exit outlet.
• The system bolts directly to the factory OEM downpipe/J-pipe using the factory flange connection. No adapter is required for OEM downpipe installations. When using an aftermarket downpipe, verify flange compatibility; a Grimmspeed DP-to-catback adapter is commonly used as a precautionary measure with some aftermarket downpipe configurations.
• This is the stainless steel muffler variant (-01). The titanium muffler and titanium tip variant is available separately as RK-C1076S-01T. Both share the same piping, fitment, and sound character; the muffler material and tip appearance are the only differences.
• Fits the VA chassis WRX and WRX STI sedan body style. The VA hatchback WRX (sold in some markets outside North America) uses a different chassis geometry at the rear and is not the intended application for this part number.

Features

• R1-Spec single-exit cat-back design - the R1-Spec designation identifies Remark's maximum-performance cat-back layout, engineered with straight-as-possible routing, minimal bends, and no resonator to minimize exhaust back pressure from the downpipe all the way to the single exit tip; the straight-through layout maximizes exhaust gas velocity and scavenging effect, contributing to improved exhaust flow efficiency compared to the factory dual-exit system with its tortuous routing, resonators, and mufflers
• Single-exit conversion from factory dual-exit - the factory VA WRX/STI uses a dual-exit rear exhaust that exits on both sides of the rear bumper; the R1-Spec cat-back consolidates the exhaust to a single center-exit configuration, which is a common preference among track enthusiasts for its cleaner rear appearance and the visual clarity it provides for bumper and rear diffuser modifications; the single-exit design also simplifies the muffler and piping layout, contributing to the weight reduction benefit
• 3-inch piping throughout - the 3" pipe diameter is an upgrade over the factory exhaust piping diameter, providing greater cross-sectional area for exhaust gas flow; the larger bore reduces velocity-based back pressure that limits exhaust scavenging efficiency, particularly at higher RPM where the factory EJ257 and FA20DIT generate their peak power output; larger bore piping is standard practice in track-oriented exhaust designs where top-end flow is prioritized over low-RPM velocity tuning
• 4.5-inch stainless steel exit tip - the single 4.5" tip provides a visually prominent single-exit appearance at the rear of the vehicle; the stainless steel tip maintains its bright, polished appearance with normal cleaning and is resistant to the surface oxidation and rust that affects painted or plated steel tips over time in the exhaust heat environment
• No resonator - the R1-Spec omits the resonator section that the factory exhaust and many aftermarket cat-back systems use to attenuate specific frequency ranges in the exhaust sound; the absence of a resonator allows the full exhaust note character of the EJ257/FA20DIT to pass through to the tip, producing the deeper, more authentic Subaru rumble that track-oriented drivers seek; this also removes a flow restriction point and reduces system weight compared to resonated alternatives
• Stainless steel muffler - the muffler canister in the -01 variant is fabricated from stainless steel; the stainless construction resists the extreme cycling heat from cold start to operating temperature that causes carbon steel mufflers to corrode from the inside out via exhaust condensation; the stainless muffler provides long service life without the internal rust perforation that is the primary failure mode of factory and budget aftermarket mufflers
• Full 304 stainless steel construction - all piping, flanges, hangers, and tip components are fabricated from 304 stainless steel for corrosion resistance in the wet, salt, and chemical exposure environment that undercarriage exhaust components experience; 304 stainless maintains its structural integrity and surface appearance over the life of the exhaust without the rust, scale, and discoloration that degrades lesser materials
• Hand TIG welded - all joints, flanges, and tip attachments are hand-welded using the TIG (tungsten inert gas) process, which produces stronger, more precise, and visually cleaner welds than MIG welding; TIG welds are also fully sealed without porosity, eliminating the exhaust leak points that commonly develop at MIG-welded joints in budget exhaust systems as the welds are subjected to repeated thermal cycling
• Weight reduction over factory - removing the factory dual muffler canisters, resonators, and associated piping provides meaningful weight savings; for track applications where reducing unsprung and sprung rear weight improves handling, braking, and lap times, this is a direct benefit in addition to the performance and sound improvements

Specifications

• Part Number: RK-C1076S-01
• System: R1-Spec Single-Exit Cat-Back
• Muffler Material: Stainless Steel
• Piping Diameter: 3 in.
• Tip Diameter: 4.5 in.
• Tip Style: Single exit
• Tip Material/Finish: Stainless Steel
• Resonator: None
• Material: 304 Stainless Steel throughout
• Welding: Hand TIG welded
• Downpipe Compatibility: OEM factory downpipe/J-pipe (direct bolt-on); aftermarket DP may require adapter
• Factory Exhaust Replaced: Full cat-back (midpipe, resonator, mufflers, tips)

Included Components

• Midpipe assembly (stainless steel)
• Stainless steel muffler canister
• 4.5 in. stainless steel single-exit tip
• Mounting hardware and adjustable hanger clamps
• Flange gaskets

Product Description

The Remark RK-C1076S-01 is the R1-Spec Single-Exit Cat-Back Exhaust with stainless steel muffler for the 2015-2021 Subaru WRX and WRX STI (VA chassis). The R1-Spec is Remark's track-oriented cat-back design, built around a 3" pipe diameter, no-resonator straight-through layout that maximizes exhaust flow from the downpipe flange to the single 4.5" stainless tip. It converts the factory dual-exit configuration to a single center-exit, a change that both simplifies the rear of the car visually and reduces system weight by eliminating the additional piping, resonator, and muffler canister required for the dual layout.

The sound character produced by the R1-Spec sits between a stock exhaust and a muffler-delete axleback. Customer reviews consistently describe it as a deep, warm Subaru rumble that is substantially louder and more characterful than factory while remaining civil enough for daily use - less aggressive than a muffler delete or resonator-delete axleback, but with the authentic EJ/FA exhaust note that enthusiasts want. Some light drone is present at highway cruise RPM, which is typical for non-resonated cat-back designs. The absence of a resonator is the primary driver of this character - it allows the full exhaust frequency range to pass through to the tip without attenuation.

All piping and components are fabricated from 304 stainless steel and hand TIG welded for long-term corrosion resistance and structural integrity. The system bolts directly to the OEM factory downpipe/J-pipe with no adapter required. The titanium muffler variant (RK-C1076S-01T) is available for owners who prefer a titanium muffler canister and the blue-tinted titanium tip aesthetic.