Core made of High-Carbon AISI 52100 Chromium Alloy Steel features higher wear resistance, fatigue strength and steel hardness, Premium quality MolyPro™ NLGI Grade 2 Molybdenum Grease (MoS2) to minimize wear and reduce friction providing longer lasting performance, Exclusive multi-lip seals are made with ProSeal™ Nitrile Rubber (NBR) which can successfully function at high delta of temperatures while retaining its flexibility and sealing performance, Inner rings are made of Case-Hardened Steel for improved resistance to surface wear and contact fatigue, Thickness and metallurgy electronically validated for manufacturing consistency, SAE J1714, J2525 and J2535 validated for OEM load-carrying capacity, durability, and performance characteristics, Part Reference Numbers : 1410-45258 WE60997 91-45258 94-45258 S510019 NT510019 WH510019 H510019 510019 FW136 TRB-510019, Part Reference Numbers : 1410-45408 WE60636 91-45408 94-45408 S510020 NT510020 WH510020 231020 H510020 510020 FW167 TRB-510020, Kit Includes: 2x Front Wheel Bearing (Both Side) + 2x Rear Wheel Bearing (Both Side)