Below is a general manufacturer product group description. Please note the information below is not item specific. Item specifics are above in product details.

In 2002 ALTA Performance was the first manufacturer to design a two piece, taper fit Mini Cooper Supercharger Pulley. Today, It is the most imitated design on the market. Our latest version of the ALTA pulley has taken pulley design to the next level. Installation is easier than ever, and the results are even more fantastic.
The ALTA supercharger pulley will increase your MINI ’s horse power by 20WHP. No additional modifications to the engine or ECU are required.
The ALTA supercharger pulley features a stainless steel supercharger shaft coupler with installation site aperture and direct torque technology. The ultra light aluminum body decreases rotational inertia and overall weight. Over-sized belt retainers and grooved teeth increase belt grip. A decorative end cap faceplate provides a clean sleek look.
Power
With the simple installation of this pulley and no other modifications boost is raised 3-5 psi and engine output by 15 to 20 horse power. No other modifications to ECU required. Customers with other existing modifications, such as Cold Air Intake, Cat-Back Exhaust, or Crank Pulley will see even better results! Regardless the first time you hit the gas pedal, you will immediately feel the difference!
Pulley Size
ALTA Pulleys are offered in two sizes: 15 and 17% reductions. The 15% pulley is the market standard and produces smooth, safe power increases. For those seeking a bit more power, the 17% is the ideal choice! Builds boost at lower RPM’s giving you even more power down low where you need it, combined with another 1.5 lbs at redline gives you the extra HP to conquer even the toughest challenge!
Ease of Installation
Simply lift the engine, remove stock pulley using the ALTA Version 2.0 pulley puller and slide your new ALTA Performance Version 2.0 pulley directly onto the supercharger shaft. Tighten the bolts, lower the engine back into place and your done! (Yes this has been simplified a bit, but click above and download a set of our highly detailed instructions. See below for the needed special puller.) There is no longer reason to remove the entire supercharger to pull off and press on a pulley.
Design-Body
The ultra light weight 6061T6 aluminum pulley body decreases rotational inertia and overall weight. Over-sized belt retainers and grooved belt teeth, preventing belts from jumping off, and increase belt grip. Cooling holes are drilled into the belt retainers to keep pulley temps in check. A decorative end cap faceplate provides a clean sleek look. Our pulley body and shafts are balanced to within .02 grams (even better than stock.)
Design-Shaft Coupler
The ALTA Performance SuperCharger pulley features a stainless steel supercharger shaft coupler with installation site aperture and we are the first to offer Direct Torque Technology( DTT ). The end of our shaft coupler is open and allows you to visibly see that the shaft collar is fully seated. DTT grips the supercharger shaft better then any press fit pulley and will work for those consumers who have had other pulleys slip and cause damage to the supercharger shaft. Our hub will attach to supercharger shafts that have been worn down as much as .020”.
DTT allows the use two different materials (stainless steel and aluminum) without having problems with the different expansion rates of such metals. ALTA again takes pulley technology to the next level. With Ten-Years Experience with MINI Performance, you can always expect the best with ALTA!