This Large Pratt set is made up of 11.5 inch long probes which are very similar to our 8 inch hegar set. The sounds are made of stainless steel. Each probe in the series is slightly larger than the one before, and slightly larger on one end than on the other, for a total of 16 graduated sizes. Sizes range from 15 french to super large 45 french(.5 inch wide). The original intended medical use for these probes was to dilate the cervix, but they were also used to clear blockages in the urethra. The tubes are rounded at each end, and they come in a high-quality, zippered black or red leather case velvet lining inside.