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 63.5g & 68g 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.
63.5g & 68g - Starts 8-10g lighter than normal at the key press until actuation, then exponential force afterward. Bottom out is the same as linear springs.
Force Curve Graph