They're plastic sealed ball bearings, that provide smooth rotation, great accuracy of accessory and even simplified upkeep.
• 1050 (3mm Thick) Sealed Ball Bearings x2
• Applications include Tamiya R/C models with double cardan joint shafts with the exception of Item 42363 (Axle Shafts for TRF420 Double Cardan Joint Shafts (2pcs.)).
• utilizing ball bearings rather than synthetic and steel bearings gives more effective rotation and better components setup.
• These ball bearings use blue plastic seals in the place of metal people – this enables you to open the bearings to completely clean and focus on them. Blue plastic seals also vastly assist in the prevention of debris entering the battle roller.
• Low-viscosity oil is employed to lubricate the interior workings.
• occasionally perform maintenance particularly including oil; after crashes, checking bearing motion is advised.