Purchased a Full size for a Full size guest bedroom to protect the 8" memory foam mattress.  Corner straps fit well but can't comment as to if the straps accommodate a 12" or thicker mattress . This mattress type does not have movement that will dislodge corner straps so it will stay in place. Washed and dried well on medium heat with no shrinking. Item is thinner than other mattress pads I purchased but this is not so much to add "Cush" as to protect against moisture getting to the mattress from any possible mishap. No crinkly noisy under the sheets so does the job and  keeps the guest mattress clean and comfy for all.