Comforters are sized larger than the corresponding bed size to allow the bedding to drape over the bed edges. A twin comforter measures 64” x 87”; a queen comforter (or full size comforter) is 87” x 87”; a king comforter is 101” x 90”; and a California king comforter measures 106” x 90”. Comforter sets include pillows or shams (pillowcases). Fill power is a measure of the loft or fluffiness of the down in down comforters; the higher the fill power, the more air an ounce of down traps and the higher the insulation. Fill power is found by placing a weight on top of down in a cylinder and measuring the space it occupies. Comforters with fill powers over 750 cubic inches per ounce are the highest quality, and such down is harvested by hand from a select number of birds. A down comforter with a rating of 700 will be lighter than a comforter with a 500 rating yet be the same in warmth. The down traps air which produces insulation, and the thickness of the layer is the loft, which increases with fill power. A higher fill power comforter hence does not need as much weight due to its thicker down. Diminished fill power can be restored by gently washing comforters and drying them, using moisture and warm air to open the matted down clusters. Down from Eider ducks has the highest fill power at 1200. The thread count of a comforter cover indicates how sealed the filling will be and hence durability and cleanliness of the comforter. Thread count is the number of threads in a square inch of fabric. Higher thread counts result in finer fabric and better sealing ability of bedding. Counts of 200 and higher are considered percale. Baffle box stitching is composed of internal walls connecting the top and bottom covers of comforters which holds the filling in place, enabling it to attain maximum loft and giving the comforter added strength and flexibility.