2-20pcs G5 Precision Ceramic Bearing Balls 1mm 15mm 2mm 25mm 3mm 35mm 4mm 5mm 6mm Si3N4 Silicon Nitride Ball-These ceramic bearing balls are great for applications were there will be extreme rotation and a premium performance bearing ball is required to meet the demands.-Lighter and stronger than tungsten carbide, these silicon nitride balls are diamond polished and guaranteed not to shatter or melt in the most extreme conditions.-Higher hardness than chrome steel balls. Vickers hardness up to 1700HV.-Specially useful for bicycles, casters, drawer slides, door locks and many other applications.Suitable for a range of purposes, some of the most common are listed below:-1/8" is often used for clusters and old English-style headsets-1/4" is often used for rear wheels and bottom brackets-3/16" is often used for front wheels-5/32" is often used for headsets with pressing cupsSpecification:Precision: G5Material: Silicon Nitride (Si3N4)5mm 12pcs2mm 10pcs1.5mm 10pcs3.5mm 10pcs2.5mm 10pcs6mm 10pcs4mm 10pcs1mm 10pcs5mm 2pcs3mm 5pcs2mm 20pcs1.5mm 20pcs3.5mm 20pcs2.5mm 20pcs6mm 5pcs4mm 5pcs1mm 20pcs5mm 4pcs3mm 10pcs2mm 8pcs2mm 25pcs3mm 25pcs