Set of 4 Even if you forget to put the cap on, the pen tip won't dry out. You can work for long hours with the cap off all day. Because the pen tip doesn't dry out, you can create posters and POP displays without worrying about opening and closing the cap, even for long tasks. The ink uses an alcohol-based formula that suppresses odors, making it gentle on people. You can also refill the ink and replace the pen tip, making it reusable and economical.