MR105 Miniature Deep Groove Ball Bearing – 5x10x4mm, Chrome Steel, High Precision. Available in open, double-shielded (ZZ) and double-sealed (2RS) configurations. Low noise, low friction, high speed. Ideal for RC cars, helicopters and aircraft, 3D printers, motors, fans, medical devices, robotics, and precision instruments. Model: MR105 / MR105ZZ / MR105-2RS Inner Diameter (d): 5 mm / 0.1969 in Outer Diameter (D): 10 mm / 0.3937 in Width (B): 3 mm, 4 mm Number of Balls: 7 – 8 Mass (approx.): 0.001 – 0.00129 kg (1 – 1.29 g)