From Longman Dictionary of Contemporary Englishring binderˈring ˌbinder noun [countable] British English 
a file for holding papers, in which metal rings go through the edges of the pages, holding them in place
a file for holding papers, in which metal rings go through the edges of the pages, holding them in placeExamples from the Corpus
ring binder• It is presented in an A4 ring binder and each section is well indexed.• At other levels materials will fit into a larger format ring binder, possibly Deskfax.• At the Survival level, packs of loose-leaf materials will be available to fit into a Filofax/Organiser ring binder. 