For some families there is no text file and may not be driven by a Type .txt file, in this instance there are 2 sizes so probably this was created and provided by Autodesk as a Generic Example family for users to adopt and edit as required unlike the Steel Framing and column Families which have more more specific dimension references in the industry.
I would ALWAYS recommend looking for manufacturers content first and contact them if not available, however there are times where you may have to use a generic family or another manufacturers content and edit as required using a data sheet to change values and fill in blanks.
Jay Colcombe
Autodesk Certified Instructor
Revit Architecture & Structure Certified Professional
AutoCAD Certified Professional
B.Sc. Hons Civil & Structural Engineering
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