I have a Shimano SORA Triple Crankset that is brand new. FC-3301
Has a 30T inner ring, but no middle or large ring. These were taken for another bike. (the crank set was cheaper than the chain rings)
Suit Shimano OCTALINK bottom bracket and 170 mm cranks.
So if you're thinking of changing your crankset to a triple, swap your double chain rings onto this crankset for a cheap conversion.
Comes with 5 new chain ring fasteners and new crank bolts (for Octalink)
Cost $30 plus postage.
I have a 52T large chain ring, little use that I will include as well.