1.用于測量內徑尺寸 For internal measurement. 2.帶可換測頭,測量范圍大 Changeable anvils for wide measuring ranges. 3.配φ57mm普通表圈百分表 Equipped with a φ57mm dial indicator. 4.百分表完全用堅固的防護罩保護 With indicator protective cover.