The most popular cover on the market! Welded wallets available in over 250 sizes and adjustable to fit every thickness of paperback book. A major feature is the rebated tongue enabling the flap to be tucked underneath the rear strap on the back cover. Adjustable Lyfjackets can also be fitted to hardbacks. To choose your Lyfjacket simply measure the height of the book and select the Adjustable Lyfjacket or the next largest from the list below. Order next size up for hardback books without dust jackets.