1. Product Overview The 31318J2/DF duplex tapered roller bearing is factory pre‑ground and face‑to‑face (DF) matched set with J2 optimized roller profile. DF face‑to‑face arrangement delivers good angular misalignment tolerance and bears combined radial and bidirectional axial loads simultaneously. Pre‑matched assembly eliminates manual pairing error for heavy‑duty rotary shafts requiring preload setting. It is widely used for heavy gearboxes, mining reducers and engineering