Fountain pens with medium (M) nibs are a popular choice among fountain pen enthusiasts and writers. Here's what you need to know about them:

1. Nib Size: The "M" in M nib stands for "medium," referring to the size of the nib, which determines the width of the lines the pen produces. M nibs typically create lines that are wider than fine (F) nibs but narrower than broad (B) nibs. They strike a balance between fine precision and smooth writing.

2. Line Width: Fountain pens with medium nibs typically produce lines that are around 0.7 to 0.9 millimeters wide. This line width is suitable for various writing tasks, making it versatile for both everyday note-taking and more expressive writing.

3. Smooth Writing Experience: M nibs are known for their smooth and consistent writing experience. They glide across the paper without requiring much pressure, which reduces hand fatigue during extended writing sessions.

4. Ink Flow: The ink flow of an M nib is generally moderate. It's sufficient for most writing styles and doesn't produce excessively thick or thin lines. This balanced ink flow contributes to the smoothness of writing.

5. Ink Variety: Fountain pens with medium nibs allow you to explore a wide range of ink colors and properties. From vibrant and bold inks to more subtle and professional options, you can find the perfect ink to suit your personal style and writing needs.

6. Paper Choice: When using fountain pens with medium nibs, it's advisable to use high-quality, smooth paper to enhance the writing experience and prevent feathering or bleeding of ink.

7. Versatility: M nibs are versatile and can be used for various writing tasks, including journaling, letter writing, note-taking, and sketching. They strike a good balance between precision and expressiveness.

8. Maintenance: Like all fountain pens, those with medium nibs require regular cleaning and maintenance to ensure optimal performance. Flushing the pen and keeping it free from dried ink is essential for smooth writing.

9. Nib Material: Nibs can be made from various materials, including stainless steel, gold, or other alloys. The material can affect the flexibility and durability of the nib.

10. Nib Customization: Some fountain pen enthusiasts choose to have their nibs customized to their preferences. This can involve adjusting the nib's flow, smoothing it, or even changing the nib size.

In summary, fountain pens with medium (M) nibs are a popular choice for those seeking a balance between line precision and smooth writing. They are versatile, suitable for a variety of writing tasks, and can be paired with a wide range of ink colors. When well-maintained, they can provide a satisfying and enjoyable writing experience.