Enduro ABEC 5 bearings use LLB type seals and our new LLU/LLB seals. The LLB seal is a light contact double lip groove seal. Grade 5 Chromium Steel Balls are within 5/1,000,000″ round. These are military level specification, used for precision equipment. R-64 hardness, of the highest grade. 52100 High Carbon Chromium Alloy Races, mirror polished to ABEC 5 precision. Nylon/Graphite or 1022 steel ball retainers.