The Class KR (B71354R) is a JQR-certified rear section exhaust designed for the Subaru WRX STI (6MT) and WRX S4 (CVT).

As a compliant, direct-fit replacement for the stock rear muffler, it delivers a deeper, sportier exhaust tone and a distinctive dual slash-cut tailpipe aesthetic, all while adhering to strict road noise regulations.

Product Highlights

🔰 OFFICIAL JQR CERTIFICATION FOR SELECT MODELS
This rear section carries official JQR certification (JQR20152009), validating its performance and legal compliance for specific WRX STI and WRX S4 grades. It is engineered to meet Japan’s 2010 Acceleration Noise Regulation, ensuring a guaranteed street-legal modification.

🔊 SPORTIER, LEGAL EXHAUST NOTE
Provides an enhanced auditory character for each platform, with sound levels certified within legal limits:

For WRX STI (EJ20 2.0L Turbo):

• Nearby Exhaust Noise: 90 dB

• Idling Noise: 68 dB

For WRX S4 (FA20 2.0L Turbo):

• Nearby Exhaust Noise: 88 dB

• Idling Noise: 63 dB

This delivers a more engaging driving experience with a noticeable yet refined increase in exhaust presence.

🔧 DIRECT BOLT-ON REAR SECTION
A straightforward 2-piece “rear piece only” system. This design allows for a simple installation process, directly replacing the OEM muffler to provide an immediate upgrade in sound and aggressive styling without modifying the center pipe.

🏗️ LIGHTWEIGHT WITH AGGRESSIVE SLASH-CUT STYLING
Crafted from durable stainless steel, the system offers a weight saving over the stock unit and features signature dual slash-cut tailpipes:

• System Weight: 12.4 kg (OEM reference: 14.7 kg)

• Weight Reduction: Approximately 2.3 kg

• Features dual-wall (W) construction with 96mm slash-cut exits for a pronounced, motorsport-inspired look.

Technical Specifications & Application

This is a JQR-certified, street-legal stainless steel rear exhaust section for specific Subaru WRX STI and WRX S4 models.

Key Details

• Product Name: Class KR Rear Piece Only [’10 Acceleration Noise Regulation Compliant Model]

• Product Code: B71354R

• JAN Code: 4512355209541

• Stock Status: In stock

Vehicle Compatibility
WRX STI (6MT)

• Chassis: CBA-VAB (Acceleration noise regulation applicable vehicle)

• Engine: 2.0L Turbo (EJ20)

• Drivetrain: 4WD (AWD)

• Grade: STI (including Type S)

• Transmission: 6MT

• Model Years: August 2014 – April 2020

• Note: Not JQR-certified. Fitment for S207, S208, and TYPE RA-R models is not confirmed.

WRX S4 (CVT)

• Chassis: DBA, 3BA-VAG (Acceleration noise regulation applicable vehicle)

• Engine: 2.0L Turbo (FA20)

• Drivetrain: 4WD (AWD)

• Grade: 2.0GT(-S) EyeSight, STI Sport EyeSight

• Transmission: CVT

• Model Years: August 2014 – March 2021

• Note: Cannot be installed on tS or STI Sport # models.

Construction & Dimensions

• Material: All Stainless Steel

• Pipe Configuration: 50×2 (Dual-pipe design)

• Tailpipe Diameter/Style: 96 mm (Slash-cut)

• Exit Direction: Dual, Left & Right (Dual-wall)

• Number of Sections: 2

• Unit Weight: 12.4 kg

• Packaging Size: 1200 × 300 × 350 mm

• Packaging Weight: 16.9 kg