These new 1.71g clutch shoes are slightly lighter than the stock aluminum shoes, allowing the engine to spool up a bit more before the shoes grab the flywheel. The end result is a clutch that will engage later in the powerband giving more rip out of the corners.
Product Update: This product was updated and now will fit also the #358582 Clutch Springs 1.1mm. The new clutch shoes are labeled Alu Clutch Shoes - Light 1.71g for 1.1mm Springs (3) or Alu Clutch Shoes - Light 1.71g - CNC Machined (3).