Sandy! Thank you! Great material.It’s not the official description, but a very good one with dimensions of the helmet. It is described in the following book from 1906:
Die Organisation, Bekleidung, Ausrüstung und Bewaffnung der Königlich Bayerischen Armee von 1806 bis 1906 - Part I
Die Organisation, Bekleidung, Ausrüstung und Bewaffnung der Königlich Bayerischen Armee von 1806 bis 1906 - Part II
Textbook (part I): Pages 209 - 211
Picturebook (part II): Pages 25 and 26
The links take you to the full book for download, but I've also attached the extracted pages for your convenience.