0.3mm / 0.35mm (Usually the same thing, just rounded down to 0.3)
0.5mm (The common fine writing thickness)
0.7mm (Common writing thickness, stronger than 0.5)
0.9mm / 1.0mm (Usually the same) 1.18mm / 1.1mm / 1.2mm (Usually the same)
1.3mm
1.4mm
2 mm
3.15mm / 3.2mm
5.6mm