The 9 blades (O-1 Tool Steel, unhardened) offered are designed to cover all the widths necessary to create a full set of Hollows and Rounds (18 pairs). All are 8" (20.32cm) long, have a bit length of 2 3/16" (5.55cm) and are tapered from 1/8" (3.17mm) to 1/16" (1.58mm) over the total length of the blade. For information on how to choose the correct blank size, please refer to Larry William's article: The Sizing and Numbering of Hollow and Round Planes. For proper fitting techniques, we recommend Larry's DVD: Making Traditional Side Escapement Planes.
These blanks can also be used to create an almost unlimited number of profile irons. When choosing a blank, keep in mind that there is a strong relationship between the iron width, wedge thickness and other variables (presence of fence, etc). Irons cannot be returned once they have been cut or heat treated.
To accommodate a wide variety of planes each of the bits are slightly wider than one would typically expect for their tang width. One should expect to cut or grind the bit to the appropriate width. Late 19th or 20th Century molding planes tend to have irons thicker than these 18th Century style irons. Using these irons as replacements in later planes may require making a new wedge.