It would not be uncommon if you have never heard of "Part" Photo etched Frets. They are a Polish Manufactured Product Primarily sold in the European Market Place. They have a full and extensive Product list including several WWI specific Detail Frets unattempted by many other PE makers.

Most surprising however is the high quality production and extensive attention to detail. 

 

Their WWI ACFT Detail frets in Particular are unique in their construction. They often include several Sub-Detail Assemblies which combine for a total detail enhancement of the Kit.

The layered or built sub-Part assemblies are best glued with either straight Future and/or a thinned Elmers white glue wash for easy clean and strong Detail assembly.

I have taken photos of all the frets available here.  Click on the Item Name to see them.

I took detailed Photos of the 32nd Scale Fret's Instruction sheets to show you close up the Incredible level of Details included in each Set which are a typical of PART Details.  

 

Even if you have Eduard Frets for some of the same Kits. These Detail Sets are Invaluable Additions to complete an enhanced build.

 

32nd Scale PART Detail Frets

 

 

48th Scale PART Detail Frets