The manfrotto mn046mcblack expan with black metal chain inserts pair allow paper background rolls from a variety of manufacturers to be mounted into the manfrotto expan wall mount system manfrotto expan background system is one of the best wall mounting system on the market manfrotto have been making this system for many years its well made robust reliable and makes life very easy working with full length background papers the expans fit into each end of the paper core then fit firmly