Stainless steel pedal washer crank protectors keep your nice new shiny sparkly fancy cranks from getting all gouged up from the sharp pedal thread lip.

Some cranks like TA and fragile and $$$ carbon cranks have a recess around the pedal holes just for pedal protecting washers like these.

But the washers will work just fine on any crank that you don't want to get all gashed by pedals like the MKS Touring which don't have a lip at the base of the pedal threads (see pic below of the crank gashing Touring pedal on the left and a no gouge RMX pedal on the right).