Announced in March 2021, these springs have a lighter linear force until actuation and then it becomes heavier. The graph explains this a little better than I do. They are within 0.5% deviation as of October 2020.
There is no polarity on multistage springs. As SPRiT says:
"According to the Newtonians, force of object A on B = the opposite force of object B on A. It damn doesn't matter which end. You feel the pressure exactly by the pressure you press"
Each bag contains ~100 springs.
Further descriptions can be found on SPRiT's website.