The roller guides were confusing for me at first. Someone gave me one for '.325 chain' and I did not understand why it would not fit mine (.325 narrow kerf), or the .325, .063 gauge STIHL chains I had. The 'flat' style file guides worked with any chain that used that diameter file.
Over time I learned that there are at least 5 different sizes/models, and that they don't physically fit over some chains, due to the width of the tie straps, some low kickback bumpers, etc. A lot of guys really like them for those chains that they do fit.
Philbert