Smart is a neutral pen that the letters and numbers can be combined at will on a single pen. The whole set of pen contains A-Z and 0-9 letter rings. Users can DIY words to vent emotional and pressure. When lacking letters, they may exchange with others, and it brings them closer. To integrate the modularity into Smart, replace the methods of personalized patterns such as traditional printing or laser, both meet the demand of users for the customization products, and solve the difficulty that the customized products can’t be batch produced. A simple design, creates infinite possibilities.