Abstract: The booklet has a refillable binder in which there are writing sheets and opened envelope-forming sheets with a gummed perimeter region bound to the cover by demountable binding rings passing through slots in a stub section. Each sheet and each envelope is separable from the stub section by a perforated tear line. The sheets, as well as the envelopes, are provided with embossed fold lines such that with a sheet lying on an envelope, the folding of the sheet and the folding of the envelope about the sheet can be done simultaneously. Sheet and envelope are torn in assembled form from the binder in a single tearing motion along a perforated line. Another perforated line is provided along one end of the envelope for opening after it is sealed.Also described is a plastic binding ring which is made up of two identical halves of extruded plastic having interlocking butt joints which snap together.