These are high quality stainless steel SPRiT Progressive springs, they provide a unique typing experience by starting off lighter at the key press and getting exponentially heavier on the downstroke.
This provides a softer, bouncier bottom out and overall pleasant feel. Available in 55g, 63.5g, 68g, 72g, 78g & 100g weights, each pack comes with 100 springs.
See below information from SPRiT on the different spring weights and force curve graph for different spring types.
Starts 8-10g lighter than normal at the key press until actuation, then exponential force afterward. Bottom out is the same as linear springs. It does not matter how you orient the spring.
Force Curve Graph