Twin XL Size Wool Mattress Topper. One inch thick genuine wool mattress topper or wool mattress cover as it is more commonly called. Wool is the ultimate in softness and support. Wool provides supreme relaxation because the crimp in the wool fiber are springy to the touch and actually act like millions of tiny soft springs almost levitating your tired body and helping to avoid pressure points that both hurt your sleep and hurt your body. Wool also is cool in the summer and warm in the winter, allowing fresh air flow and moisture control. Plus, wool can absorb moisture and still feel dry. How can you ask for a better mattress pad?