I love these for mailing soft paper products etc. but they do NOT guarantee the Postal Service will NOT BEND...just think first and check before mailing if essential not to bend paperback books etc. Would be nice to have more info on the sales tags about bendability and mailing issues. I had a small 8.5 x 11 " paperback book to mail but they told me the machines at U.S. Postal Service would bend them the WRONG way...had to pay more postage and it would have been better (cost-efficient) to buy the rigid envelopes... a learning experience!