When it comes to finding the perfect fountain pen for your writing needs, the nib size is an important factor to consider. A fine nib fountain pen produces a thin line that is great for detailed writing, while a medium nib fountain pen produces a thicker line that is ideal for larger handwriting. Depending on what type of writing you plan on doing, it is important to take this into account when selecting your fountain pen. A fine nib fountain pen might be best for doing paper work or essays, while a medium nib fountain pen might be best for creating art or taking notes in class. Ultimately, the choice is yours and both can certainly create a great writing experience.