And to clarify further (assuming you mean SPD "mountain" pedals (which lots of people are using on road bikes), there seem to be 3 kinds (with inconsistent labeling):

- Dual sided (i.e., the kind you can clip into on either side) -- they make these with or without a surrounding platform

- Double sided (or Two sided) (i.e., the kind where you can clip in on one side, or ride it like a platform pedal on the other

- Single sided (i.e., the kind where you can clip in on one side and can't do much of anything with the other side) -- these tend to be the lightest in weight

Within each type, Shimano seems to offer 3 levels (let's call them Good, Better, and Best). The more you pay, the higher the quality of construction and the lighter the pedal.

If you go to the Shimano website, you can see all their offerings. Or if you pretty much know which type you want (and how much you want/are willing to pay), I'd be happy to suggest one. And other folks will suggest others!