The base and bolster sides of the Ultima bed are really special. At the core is a dense foam for stability and support. Bonded fibre is then wrapped around the foam core to add a softer layer for comfort and shape. A Polycotton inner cover zips over the structure to hold it in place and is removable for easy washing. The cover is zippered and easily removable for machine washing. Simply turn the bed inside out, take out the zipped inserts and wash just the cover, just the inserts or both. Size Guide: - Small: External (width x depth x height) 59cm x 54cm x 28cm (23" x 21" x 11"), Internal (width x depth x height) 36cm x 31cm x 20cm (14" x 12" x 8") - Medium: External (width x depth x height) 74cm x 66cm x 28cm (29" x 26" x 11"), Internal (width x depth x height) 51cm x 44cm x 20cm (20" x 17" x 8") - Large: External (width x depth x height) 84cm x 79cm x 31cm (33" x 31" x 12"), Internal (width x depth x height) 66cm x 56cm x 23cm (26" x 22" x 9") - X Large: External (width x depth x height) 100cm x 86cm x 36cm (39" x 34" x 14"), Internal (width x depth x height) 80cm x 65cm x 24cm (31" x 26" x 9")