 The flat drains are measured in millimeters, and the round drains are measured in French sizes.Patients or caretakers can "strip" the drains by taking a damp towel or piece of cloth and bracing the portion of the tubing closest to the body with their fingers, run the cloth down the length of the tube to the drain bulb.One can also put a little bit of lotion or mineral oil on their fingertips to lubricate the tube to make stripping easier.