A.160~190kPa B.170~190kPa C.160~200kPa D.170~200kPa
A.1mm B.2±0.5mm C.2mm D.0.5mm
A.15mm×15mm,10~15點接觸 B.20mm×20mm,15~20點接觸 C.25mm×25mm,20~25點接觸 D.30mm×30mm,25~30點接觸