Bucky Balls 1) Different size: 3mm,4mm,4.8mm,5mm,6mm...10mm 2)COlor: NI,BLACK-NI,GOLD,SILVER, AND ... N35 or N38 Neodymium magnet balls.Diameter: 4mm,4.8mm,5mm,6mm,7mm,8mm,9mm,10mm(tolerance+/-0.02mm)Color: gold, silver,black ... nickel, blue, red ,yellow ,green ,orange or othersMagnetic force(N35grade):5mm ...