Sizing is edge-to-edge, not interior fit

I love the tiled design of my logo on these mailers, but was disappointed with the size. I ordered 50 of the 5" x 9" envelope (special pricing deal) thinking it would fit one of my books and then ordered a smaller amount of the 7.5" x 10" thinking they would fit my larger books, but now I have 50 envelopes that won't fit any books and 20 that will work with only one of my books. I would order (and will order) again because I like the design. However, be aware of interior size fit for items vs the actual size of the mailer and bump up by at least 2" all around.