C.O.M. stands for Customer’s Own Materials
Pronounce just the letters C-O-M. This is not necessarily the “customer’s” materials but rather materials other than what the manufacturer can provide. Depending on the manufacturer there may or may not be an upcharge for using your own fabric or materials.
Designers like to use C.O.M. because it makes the piece more customized and unique for their clients and the space they are designing.