Seat tube measurement for clamp?

[CRASH]

I need to buy a clamp for a 3-speed pully that will attach to the seat tube. Between 1", and 1-1/8", if I measure the outside diameter of the seat tube, is that precise enough? I'm assuming that's where those sizes are referring. I just want to make sure before I order.

 

[Karate Chicken Industries]

Yes, OD of the seat tube is correct for that measurement.

 

[RustySprockets]

Sounds reasonable. I can't imagine you need anything more than the OD of the tube you wish to mount to.

 

[rickpaulos]

And those are the two available sizes. 1 and 1 & 1/8".
1" is common on old ef Schwinns and USA made bikes.
1 & 1/8" is common on lugged frames.