This plastic sleeve is 5″ long with the 2″ or 2.5″ O.D. (outer diameter). Commonly used to connect the nozzle and the flex hose, but may also be used to connect two hose sections however it is more common to use aluminum hose splices for hose sections.
The Expander sleeve is used for one last agitation before material exits through the nozzle. (notice the two bends/indentations)