Enduro Bearings - Enduro ABEC5 bearing 17287 LLB 17x28x7mm 13.6g

Balls:
Grade 10 Chromium Steel Balls:
High precision balls are within 10/1,000,000″ round, twice as round as the industry standard, at it’s highest level.

Races:
52100 High Carbon Chromium Alloy Races.
Vacuum de-gassed process for the purest chromium alloy steel, hardened to R-62, extremely tough and very durable. Polished to a mirror finish for ABEC-5 precision and noiseless movement.

Retainers:
Riveted Steel Retainer for toughness, ABEC-5 tolerances and noise tested, C-3 or C-N Internal Clearance

The ABEC-5 Standard:
ABEC ratings are standards which require each bearing to pass many tests in order to meet the scheduled requirements. This includes noise testing at high RPM, extremely tight tolerances for the internal diameter, outer diameter, roundness of ball, trueness of races, and surface finish of all of the above. The ABEC 5 rating is a good rating for use in bicycles.

Seals:
Two NBR 70 rubber LLB Dual-Lip seals with low contact type seal, which rides in a matching groove machined into the bearing.