Perfect for tucking in your pocket or purse, so thin and flexible, but strong--they hold up well. Sort of a versatile "diary" to record random information. I like the plain (no lines) so I can draw a diagram or write small or large or whatever. Since this slips so easily into almost anything I carry, I always have something permanent to make a note in, which is easily retrieved later.  And the pocket on the back inside cover can hold business cards, stamps, etc..