The screw pitch can be changed without limit in the twin screw extruder. There are, however, practical limits. The number of flights can be varied; but, most typically, this is set at either one, two, or three. Cut flight screws can be used at any position in the barrel. For each specific twin screw extruder, these is a fixed shaft to shaft center distance and a fixed screw diameter, therefore, there is a fixed screw root diameter which results in a fixed flight depth. This flight depth will vary from manufacture to manufacture.