Big Sur by Wendy BellissimoItem #: 4920-9500 75W x 21D x 13H On casters. Use with the 4920 Panel Bed, Bookcase Bed, Bunk Bed or Bunk Bed with extension under the bed rails. Takes a standard foam trundle mattress (max size: 73x38x8) for use as an extra bed or two removable dividers (included) allow for organized underbid storage option. Requires Bed Rails. Rails must be in the high lock position.