This is a two-way pet bed. By tightening the string, it becomes an enveloping shape. By loosening the string, it can be used as a mat. When the string is loosened: Diameter 55cm (Please allow for some margin of error) It also allows for size adjustment, so it can be comfortably adjusted for cats, dogs, and other small animals. It has a warm fleece outer fabric and is filled with resilient cotton. ⚠️ Although it is quilted, the ends of the sewing threads may stick out. If they get caught on small paws or feet, it could cause injury. Please tuck them back inside the fabric as soon as you find them, or after treating them to prevent fraying, cut them with scissors!