2010 Triumph Thunderbird Boss slip-ons, Number 557-12.

Experience an immediate 10% increase in low-end Torque. Our Boss Slip-ons utilize stock heat shields and are a snap to install.

We've modified the mounting so that they shoot out the back perpendicular to the rear wheel... giving it a custom look.

Must use triumph download #020359.

Even more power increase is expected with hi-flow air cleaner (none available at the time of testing).