Double Venturi - can be thought of as two nozzles in series with a gap and holes in between to allow the insertion of atmospheric air into the downstream segment. The exit end is also wider than a conventional venturi. Both modifications are made to increase the size of the blast pattern and minimize the loss of abrasive velocity. Wide Throat - features a large entry throat and a large, diverging exit bore. Angle Nozzles - necessary for for tight spots like bridge lattice, behind flanges, or inside pipes.
Many operators waste abrasive and time waiting for ricochet to get the job done.
The little time it takes to switch to an angle nozzle is always quickly recovered and total time on the job is reduced.