The 68-SS-120 is a road spindle, intended for use with double chainrings. If you're using a road crank, running the chainring on the inner plateau should give you a good chainline. If you're using a track crank, you'll want the 68-P-120 spindle (unless you have an old frame with 110mm rear dropout spacing, in which case you'll want the 68-P-110).