A.0.05mm B.0.1mm C.0.2mm D.0.3mm
A.0.1~0.5mm B.0.5~1.5mm C.1.5~2.5mm D.2.5-3.5mm
A.大孔 B.小孔 C.等徑孔后擴大孔 D.大小孔沒先后