Simple pen / Simple pen

Simple pen, when the pen runs out of ink after the ink on the pen in general have a complicated process, and there was a time when the ink on a business trip forget, consider this simple pen two factors, the ink on the simplified process , just to bring a pen ink can be directly Shanghao, equivalent to the principle of the syringe. 2. Pen ink tube is transparent, how much ink left can easily see.