1. Material: GCr15 440 440c; 3. Grade: G10-- G100; 4. 3. Miniature ball: 1. Material: stainless steel (201304316316 L, 420440440 C); Bearing steel GCr15. Carbon steel 1010104, 5108, 5; 2. Specification: 0.5 mm - 2.5 mm to 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.25 mm, 1.30 mm, 1.35 mm, 1.40 mm, 1.45 mm, 1.50 mm, 1.588 mm, 1.60 mm, 1.65 mm, 1.75 mm, 2.0 mm (3) levels: G16, G100; Specification of extra-large bearing steel balls :30MM-- 152.4mm 2. Specification of special GCR15 steel balls: 30mm, 30.163mm, 31mm, 31.75mm, 32mm, 33.338mm, 34mm, 35mm, 34.925mm, 36.513mm, 38.1mm, 39.688mm, 40mm, 41.275mm, 42.863mm, 44.445mm, 45mm, 46.625 mm,