A while ago I printed a watch band by @Da9L_135090, I've worn it for about a year and a half now, but over time it has gotten a bit dirty and worn, and I wanted a new pattern. 

So I went and found the source of their design, which was Adafruit's Apple watch band. I used some boolean tricks in Blender along with arrays to create a 2D cubic pattern to cut into the watch band. I also lengthened the watch band, added three extra holes (like DA9L did in their version) and used DA9L's design of the pin hole structure. 

The most significant changes are to the actual pattern of the band, and the thickness of the band. Because it has a pattern cut into it, there is significantly less material, and it flexes more easily, so it needs to be thicker.

I've included the files for a smaller and larger wrist, if you need a different size drop a comment below! I'll also take requests for patterns if they are reasonable. 

The reason I like the patterned design instead of a solid band is because it prevents irritation from getting water under the band while washing your hands or getting sweat under it after exercise. It is very effective at allowing your skin to breathe!

Printing tips:
This band must be printed in TPU, I used 95A. Watch the first layer very carefully! All those pattern lines need to go down nicely for the rest of the band to print properly, so your z-offset must be well-tuned. 

You will need 20mm watch band pins like these: https://www.amazon.com/Release-Stainless-Replacement-Compatible-Samsung/dp/B0D59WKPQN

Please note, I did not buy them from the link above, I cannot vouch for whether they will work, I am only placing it there as an example!

I don't know exactly which smartwatches this band will be compatible with, but here's a list of some of the ones I know of:
Samsung Galaxy watch 4, 5, 6, 7
Garmin Instinct, Descent, Fēnix, Epix, Approach and more.
Pebble (some models may be compatible)

All of the above watches are untested, except for the Galaxy Watch 4. Print at your own risk!! Please let me know down below if something doesn't fit right. I have not done any research on other non-smart watches, because there are too many of them out there.

Now, the pins are difficult to put in, but it's definitely doable. Here's a quick tutorial:

1. Place the pin in the small slot in the back of the watch band, long side first, pictured below:

2. Push the pin carefully through the hole, keeping it as parallel to the hole as possible, careful not to poke a hole in the print, until you reach the point pictured below: 

3. Now, using something flat and blunt like a butter knife, push the pin through as far as you can, until the far side (long side) is sticking out the other end of the band, as seen below:

4. Finally, push the short end of the pin down into the hole. The TPU should be flexible enough to allow this. Then push the long end of the pin back a bit to get the pin centered in the hole. It should look like this: