...Now, the differences between the OB-1 and the OB-2, other than the tip diameter, are on the inside. The 2 uses a smaller core. The reason for this is simple, wall thickness. On the OB-1 we recommend a minimum diameter of 12.25mm in order to keep the wall thickness substantial enough to hold up under the impacts of play. The OB-2 uses a smaller core throughout in order to maintain that consistent wall thickness with the smaller tip size. Of course, in the middle of the shaft where the outside diameters are pretty close to the same between the 2, the 2 has a thicker wall and is therefore a little stiffer.
Your OB shaft on the left appears to be an OB-1. If that is the case, and it is smaller than 12.25, then the wal thickness is down pretty low. Although we don't recommend it, I have seen many that were under 12mm and still holding up. These shafts also had the lowest squirt or deflection of any of our cue shafts due to the reduced mass from the thinner wall thickness.....
Royce Bunnell
www.obcues.com