I pulled my original rollers and weighed them, 7 of the 8 weighed 33gr, the 8th weighed 32gr, not so much the weight as the shape, the wedge shape of the Dr Pulley allow them to get closer to the center and compress the pulley a little more and the outer wedge allows the slide to move farther out to make the variable pulley act larger (slightly higher top speed). There are other benefits, smoother transitions from stopped through the RPM range, slightly quicker take off, slightly higher top speed and this doesn't affect the fuel economy other than you want to rip it when riding...hope this helps. When I chose my Dr Pulley, I went with the 32 gr to only slightly improve the overall performance without too much affect on speed or stop light performance. Works well for me.