For an economical traditional metric spherical bearing, QA1's MCOM and MCOM-T Series is the perfect choice. Each bearing is made from chromoly steel with an optional self-lubricating PTFE liner. BALL, 52100 Bearing Steel, Heat Treated, Hard Chrome Plated, Precision Ground, , LINER (COM-T), PTFE, Self-Lubricating, , RACE, Chromoly Steel (Mfr.'s Option - Stainless Steel), Heat Treated, Protective Coated for Corrosion Resistance.