This is R31 House Aluminum M2.6x0.5mm King Pin Adjustment Spacer 4 pcs Black.
For: R31 House GRK4
An aluminum spacer with an inner diameter of 2.6 mm and a thickness of 0.5 mm.
By changing the amount of spacers sandwiched between the knuckle body and the adapter
It is possible to adjust the kingpin angle in 0.7 degree increments
R31 House Aluminum M2.6x0.5mm King Pin Adjustment Spacer (4 pcs)