A mold includes a mold core, a first cover, and a second cover. The mold core includes a cavity and a pair of elastic pieces. The pair of elastic pieces is in the cavity and divides the cavity into a first room and a second room. The first cover covers the first room of the cavity. The first cover defines a plurality of first plug holes. A first I/O can be formed in the first room by injecting a first liquid plastic material in the first room via the plurality of first plug holes. The second cover covers the first room and second room of the cavity. The second cover defines a plurality of second plug holes. A second I/O port assembly can be formed by injecting a second liquid plastic material in the first room and the second room via the plurality of second plug holes.