Beyond impeller bore configurations, with the Conn styles as well as other louvered or vented styles open area in the center of the impeller must also be considered. Typically, reinforcing discs, taper plates, sandwhich the blade to stiffen the disperser disc. Due to the louver placement on the conn blade, the size of these disks, and with small sizes - the diameter of the mounting hub, must be considered.
The below table gives approximate dimensions of the CONN Blade styles IT and ITT. The Clear Diameter (yellow column) defines the diameter of a circle clear of obstruction. The clear diameter represents the largest taper plate or hub a given size impeller can handle.