Includes (1) 2610911928 Ball BearingNew, Bulk PackedGenuine OEM Replacement Part # 2610911928Consult owners manual for proper part number identification and proper installationPlease refer to list for compatibilityCompatible with the following: Bosch models: 4000, 44, B3915 Slide, 391510 Inch Slide, 4212L Dual-Bevel Upfront Control & Laser Tracking, 5412L Laser Tracking Dual-Bevel Slide, 4410LUpfront Control & Laser Tracking Dual-Bevel Slide, 4212, 4410, 4212L, 4100, 4100DG-09 Worksite, 4100DG-09 Worksite, 4100-09 Worksite, 4100-09 Worksite, 541212 in. Dual-Bevel Slide, 541212 in. Dual-Bevel Slide, 5312Dual-Bevel Slide, 4310Dual-Bevel Slide Miter Saw. This Ball Bearing has metal shielding on both sides. This genuine Bosch Replacement part is sold individually. Ball bearings are used to reduce friction between rotating parts. The balls or rollers take the load and spin, distributing the weight evenly while the minimal contact area of the ball reduces friction. This reduces wear on the tool and allows it to run smoothly. Bearings experience constant wear when the tool is in operation from pressure, heat, vibration and friction. Because of this, many Bearings need periodic maintenance or Replacement.