Packed 21 books in box; paid for 14 lbs 4 oz (these are children's picture books, or it would be even heavier), stuffed packing material around. Another adult witnessed me pack all of them, and a third adult transferred them to the post office and confirms the box was thoroughly packed and heavy. Buyer sent photo of opened box with 17 of the books removed claiming I didn't send them, and requested a return. Since having only 4 of the books are useless to me (and I would have had to pay for the books to be mailed back! and definitely wouldn't have gotten much out of selling just those 4), I offered a partial refund, less the amount I spent on shipping + fees. They refused partial refund, demanded full refund, and left negative feedback. No attempt to claim box was damaged or tampered with during shipping, just claimed I didn't send all the books when I very well did! (I have absolutely no interest in the books back or selling them again, I wanted them gone but since they were a full set I figured I'd get something out of it. Instead, I had to pay money to give them away, and got negative feedback on my account to boot.) Also laughable: they claimed "an engineer friend" measured the box and "proved" that all the books plus the packing material wouldn't fit. (They had fit quite well, actually, some of the packing material on the side and the rest on top. And who has "an engineer friend" around to call over within a few hours' notice to measure books and tell you if they could have fit or not? Skeeeeeetchy…)