I suggest rephrasing the measurements for clarity:
1) Segment CO is 2 centimeters long, and segment OD is 7 centimeters long. 2) Segment CO is 1 centimeter and 3 millimeters long, and segment OD is 6 centimeters long. 3) The lengths of segments CO and OD are 6 centimeters each.
I suggest rephrasing the measurements for clarity:
1) Segment CO is 2 centimeters long, and segment OD is 7 centimeters long.
2) Segment CO is 1 centimeter and 3 millimeters long, and segment OD is 6 centimeters long.
3) The lengths of segments CO and OD are 6 centimeters each.