he product code B12B819721 refers to the Roller Assembly Kit 2 for the high-volume document scanners:
Epson WorkForce DS-870 (Up to 65 ppm / 130 ipm)
Epson WorkForce DS-970 (Up to 85 ppm / 170 ipm).
These components work together to ensure that documents are reliably pulled from the 100-sheet ADF stack (Pickup Roller) and that only one sheet feeds into the scanner at a time (Separation Roller).