2 outside card holders and room to store more in the center pocket....

On one side your daily calendars, on the other your to-do lists... OR
on one side your to-do lists, on the other your note cards...
However you use it, this case is 2-sided and ready for double duty in a simple slender design. 
There is room to hold several cards in each stack and the top one can be easily removed with the next one ready and waiting for your quick notes and ideas.
When you need addtional cards just take them out of the center storage pocket which holds about 15.