Carbon Suspension Pin 3.0mm Diameter (2 pieces) - 42mm 44mm 49.5mm 52.8mm  [BARELL] BRL-SH03 BRL-SH04 BRL-SH05 BRL-SH06

This is carbon suspension pins. 
It is extremely lightweight, enhancing the overall feel.
Diameter: φ3mm Length

Fitment guide (it can fit other platforms as well)

42mm - YD2 Series
44mm - YD-2 Series (Rear), GALM (Front/Rear), and RDX (Rear)
49mm - Rear of GRK4 and GRK5 chassis
52.8mm - Front of GRK4 and GRK5 chassis