Is there an average poster size?

Green Circle

I have seen a bunch of posts regarding the storage of posters. I have quite a few being stored in tubes and i would like to store them flat so I can open something up and look at them without having to worry about something spilling on them or my cat walking across them. I would love a binder portfolio or a large presentation book. From what I have found the binder portfolio largest size was 24x18 and the Large Presentation book went up to 24x36

any thoughts? I would really appreciate the help, 

Thanks! 

Kwieneke

for the last two years its been 18x24

njhaley1

https://www.baroqueportfolios.com/

Itsmillertyme

Amazon has several types. I use the Itoya 18x24 for most prints