The new Surface Pen for the Surface Pro 4 and Surface Book (which also happens to be compatible with the Surface 3/Pro 3) features interchangeable pen tips allowing users to better customize their drawing or writing experience. The four available nibs are sold separately as a $10 USD accessory and features four tips demarcated according to pencil softness: 2H, H, HB, and B.
The pen tips are housed in a gray clamping mechanism and covered with a plastic transparent glass. It's a very durable and portable transportation mechanism and I have no complaints of the housing.
Swapping tips is done through the clamp-like mechanism on the bottom of the tip kit. Clamp tightly the protruding exterior of the tip currently fastened to the pen, and pull.
Then take your desired tip and push it in until secured.
From what I've been told, some Microsoft store representatives have been able to free the standard HB pen tip from the pen using their bare finger nails. I have yet to replicate such an immense feat of human achievement and courage, at least with the thinner tips.
The hardest 2H and the most slippery, with virtually no friction when rubbing against the Surface Pro 4's screen. This, combined with the fact that it's the widest tip, in my experience, made it the most imprecise tip to draw with. It's almost mind-blowing how slippery it is; it's so slippery that it feels rather useless. I'm sure opinions will vary on this, but in my experience going from the default HB tip to the 2H is like going from driving on concrete to driving on ice. It's uncomfortably freeform. The lack of friction makes slow, controlled strokes difficult to render.
The next hardest is the H, which carries a similar slipperiness, but has a subtle tendency to grip the screen a bit tighter when changes in direction. It's a little bit more pleasant than the 2H, but that's not really saying much. It does feature a much thinner tip, which I think makes it more pleasant to use for finer drawing.
The HB tip is the default tip that comes with the Surface Pen, and it's my favorite. While it's a bit more slippery than an actual pencil on paper, it features a pleasant amount of resistance that encourages slow and careful drawing. At first I felt it added too much resistance, which made fast and loose sketching unpleasant. But as time went on I grew to appreciate it more, especially after using its harder colleagues. Like the new Type Cover, Microsoft did a great job with the standard HB.
The final B tip features slightly heavier resistance than the HB. The physical tip itself also feels "harder". Whereas the HB feels like it sways or bends a little bit when drawing heavy strokes, the B has no give whatsoever. It's basically a more rugged version of the HB tip. If for whatever reason the HB feels too flimsy, the B tip might be just what the doctor ordered.
As always, your mileage may vary. Thankfully, at only $10 USD, there's no reason not to try it, especially if the default HB pen tip feels unsatisfying.