FAQ THE MATTRESSES WILL MY SHEETS FIT ON A CASPER? SEE ALL QUESTIONS WILL MY SHEETS FIT ON A CASPER? As long as your sheets are compatible with a 12 inch high mattress, they will absolutely fit on any of the Casper mattresses! We recommend using Casper sheets for the best sleep environment possible. YOU MAY ALSO LIKE Will Casper sheets only fit on a Casper mattress? Can I use a box spring? How should I wash my sheets? What is Supima® or Pima® Cotton?