The back panel of the skirt is about 13" across - skirt is very adjustable since it fully wraps around with extra fabric to accommodate different body shapes and sizes.  Skirt is 31" long.  I do not see any size tags or fiber content tags on this piece.  Feels like a light weight satin type polyester.  Non smoking household - exactly as shown - true vintage - belonged to my mother from the 60 s or 70s