Refills for writing instruments are ink cartridges or containers that can be replaced in various writing tools, such as pens, pencils, or markers. They are designed to allow the reloading and continuation of using the writing tool once the original ink has been depleted. Refills come in different types and sizes, depending on the writing instrument they are intended for, and can contain ink in various colors and consistencies. Using refills is a convenient and economical way to keep writing instruments functional and extend their lifespan.