Refillable pens are writing instruments designed to be reused by replacing their ink cartridges instead of being thrown away. This feature makes them more environmentally friendly compared to disposable pens, as they reduce plastic waste. Refillable pens come in various styles, including ballpoint, fountain, and gel pens, catering to different writing preferences. Many refillable pens are made from durable materials, allowing them to last for years with proper care. Users can choose from a wide range of ink colors and types, making it easy to customize their writing experience. Popular brands like Pilot and Lamy offer a variety of refillable options.