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2in1 exhaust

Your riding style might get you in trouble, your exhaust won't

Explore a new dimension of customization focused on performance, not just aesthetics. Dr. Jekill & Mr. Hyde® is venturing into Clubstyle/Performance!

THE ‘TWENTY-ONE’ - A Distinctive 2-in-1 Electronically Adjustable Exhaust

After months of meticulous design, construction, and prototyping, Dr. Jekill & Mr. Hyde® proudly unveils the 'Twenty-One,' a one-of-a-kind 2-in-1 electronically adjustable exhaust tailored for all Milwaukee-Eight Softail Models.*

After months of meticulous design, construction, and prototyping, Dr. Jekill & Mr. Hyde® proudly unveils the 'Twenty-One,' a one-of-a-kind 2-in-1 electronically adjustable exhaust tailored for all Milwaukee-Eight Softail Models.* Crafted to meet the expectations of riders seeking an elevated Harley experience in terms of performance and sound, the Twenty-One caters specifically to the dynamic needs of the clubstyle/performance scene. Importantly, it retains the distinctive features and innovations characteristic of Dr. Jekill & Mr. Hyde® exhaust systems.

Get ready for an exhaust that not only delivers powerhouse performance but also boasts a sound that matches its beastly capabilities. The raw and stripped-down design of the Twenty-One makes it an essential addition to your Milwaukee-Eight Softail, combining both style and substance. Upgrade your riding experience with the 'Twenty-One' - where performance meets innovation.

*Available for Street Bob // Fat Bob // Low Rider // Low Rider S // Breakout / Fat Boy // Heritage // Deluxe // Slim

Explore the Sound Experience of the 'Twenty-One'

Immerse yourself in the unique sound of the 'Twenty-One' that elevates the power of the M8 engine to unprecedented heights. Experience the thrill of riding with a heightened feedback from your exhaust, encouraging you to push your bike a little further. The exhaust has undergone rigorous sound tests to deliver this perfect auditory experience, ensuring every ride becomes a symphony of power and precision.

Club Style Project 21

adjust your sound to the moment

three sound modes

Dr. Jekill & Mr. Hyde® systems introduce three distinctive personalities*: Dr. Jekill mode, Dynamic mode, and Mr. Hyde mode. With a simple push of a button, a valve inside the muffler seamlessly adjusts – closing, opening, or partially opening to enhance both power and sound. This provides you with versatile tools to fine-tune your exhaust sound according to the present moment.

* Blackbox systems (motorcycles without CAN bus) offer two sound modes.

Club Style Project 21 The Looks


Opt for the Twenty-One, and you'll receive a complete exhaust system featuring a header set and muffler. While our other Dr. Jekill & Mr. Hyde® exhausts boast a clean design, the Twenty-One stands out with a rugged and unpolished appearance, showcasing visible welds and a natural discoloration over time. This system is not only lighter than standard exhausts but also provides optimal ground clearance for a comfortable lean in the bends. Despite its raw aesthetic, the Twenty-One maintains the quality synonymous with Dr. Jekill & Mr. Hyde® products.

Club Style Project 21 Performance


Tailored for the clubstyle rider, performance takes center stage in the development of the Twenty-One exhaust. Compliant with legal standards, the Twenty-One substantially enhances your bike's performance. The exhaust's design eliminates performance loss when riding with a closed valve, ensuring a safe and smooth experience, regardless of the mode you choose.


Harley-Davidson, deeply rooted in tradition, stands as a brand defined by its enduring pillars. The iconic chopper, effortlessly cruising down the American Highway, has become a timeless image etched into our collective consciousness. However, as with any tradition, there arises a shift in perspective, challenging its long-standing validity.

Emerging from the motorcycle club culture, where bikers navigated extensive distances, a movement took shape—shifting the focus from customizing Harley looks to optimizing performance. Modifications were directed at making bikes faster, more manageable, and agile enough to conquer corners with knees brushing the ground. Originating with the FXR, evolving through the Dyna, and seamlessly integrating into the latest Softails.

Clubstyle has become an undeniable force in today's Harley scene. For Dr. Jekill & Mr. Hyde®, it was a natural progression to craft an exhaust specifically tailored for this dynamic movement. Collaborating with esteemed partners from the clubstyle & performance scene, we initiated Project 21: the creation of the ultimate electronically adjustable clubstyle/performance 2-in-1 exhaust!

Club Style Project 21 The Looks

Tailor-Made Options

The Twenty-One offers a range of customization possibilities. Opt for a black or brushed edition for both the muffler and header set, and choose from a variety of end cap options – slashcut or streetfighter, available in black, aluminum, or bronze. Take it a step further by selecting between a full cover of shields or a more minimal cover for the header sets. Explore our exhaust configurator to discover the design that suits you best.