The Select Comfort Sleep Number Foam Rail OEM 1 Piece fits a King size or California King Size and can fit on the left or right side. The Beige color is a medium firm mattress made of foam, designed for adult use. It features edge support and is part of the Sleep Number product line by Select Comfort. The mattress has dimensions of 84 inches in length, 4 inches in height, and 6 inches in width, making it suitable for a king-sized bed. This one-piece rail is an essential component for a Sleep Number bed, providing added comfort and support for a restful night's sleep.