reversible quilted design for year-round comfort 100% wool and 100% hollowfibre layers feels warm in winter and cool and crisp in summer elastic straps stretch to accommodate a mattress depth of up to 34cm on all sizes once you've slept with a mattress topper, you'll never dream of going without. this reversible quilted style provides a luxurious layer of year-round softness and comfort. use the merino wool side for a super-warm feel in winter, then flip it over in summer for cool and crisp cotton.