Studio-Assets Muslin for 6'x6' PXB System - BlackStudio Assets Muslin for 6'x6' PXB System Black This 6 x 6' black muslin is for use with the PXB Portable X frame Backdrop System. The PXB Solid Color Black Muslin Backdrop is constructed from 100% cotton muslin. It is machine washable on the gentle cycle using cold water and a mild detergent. The muslin is mill dyed using reactive dyes and then steam dried allowing it to be lightfast so it won't fade over time.