A standard ballpoint or rollerball refill consists of 4 components, the ball housing, the ball, the ink and the tube. Some refills also have a cap. I can't find an answer to what the "original fill" is called other than an ink supply. The tube or tubes that house the refill are called the barrel or barrels. If there is a separate section where ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.