⑴ Disposable ballpoint pen, the penholder is the refill, neither can add ink nor change the refill, if the ink is used up, it can only be discarded.
⑵ Ballpoint pen that can change the refill, with buttons, spring, lock, recovery and other functions.
⑶ The pen barrel can be rotated to extend or retract the pen core.
⑷ There are new ballpoint pens such as a combination of ballpoint pen and fountain pen, a combination of ballpoint pen and pencil, a combination of ballpoint pen and electric tester, and a combination of ballpoint pen and tiny light bulb.
