Like some electronics, this linear motion Pico servo doesn't like running at over 5V. Even slightly less is better. This adapter board adds a bit of voltage drop to a 5/6V system to make your servo happy.
The 22090 Pico linear servo is a very cool device, but really doesn't like being run over 5V. To ensure that it's kept at this lower voltage level when being used on a 5 or 6V system, we put together this inexpensive voltage-drop adapter board. It's not as good as a dedicated 3.7V regulator, but in our tests, it's worked out just fine!
You might want to get an appropriate servo cable, depending on your use!