20 sheets displays up to 40 pages of larger dimension : 229mm X 305mm (9 inch X 12 inch).
The Rondofile Plus 20 (20 sheets, black) is a specialised larger size folder with Rondofile 229mm x 305mm sheets, which are slightly larger than A4 size.
The aim of this folder is to accommodate and fit the larger sized Orchestral and Band Sheet music and scores. (Since it is larger than A4, it can also accommodate A4 music sheets.)