umm i dont have any experience with them but the UR website says that the pulleys are the same size, but that they are lightened
Why do some people feel compelled to post incorrect information?
From UR's website (unorthodoxracing.com/faq_pulleys.html) -
"Underdriving/underdrive is slowing the speed of the accessories, or the driven component, from the original speed they were turned by the OEM crank pulley. Underdriving can be accomplished in two ways. First is by increasing the diameter of the accessory pulley/s. The problem with this method is that it increases the size of the accessory pulley/s which increases their weight. Weight reduction is the most important key to increasing engine performance and response. This method also eliminates the ability to underdrive the a/c, which is a tremendous robber of horsepower.
THE SECOND METHOD, USED BY UNOTHODOX RACING, IS BY REDUCING THE DIAMETER OF THE MAIN DRIVE PULLEY OR CRANK PULLEY. By using this method we can achieve the best ratio of size reduction, underdriving, and most importantly we can maximize the reduction of weight on the crank pulley where most of the weight savings can be seen.
Weight loss is the most critical factor in making, or more accurately, releasing Horsepower! Each pound of weight taken off the engines rotating assembly is worth approximately 2.7HP and the figure increases dramatically with forced induction, nitrous, VTEC and increased RPM's. Only 15-20% of the gains seen from our pulleys comes from the underdriving. THE DIAMETER OF EACH OF OUR CRANK PULLEYS IS REDUCED UP TO 20%. We tailor the exact amount of underdrive to each vehicle based on factory specified accessory performance."