M16-2 x 55mm 內六角螺絲 | 六角驅動 | 全螺紋 | 12.9級合金鋼 熱處理黑色氧化 (50個/包)

The black oxide finish on these M16 screws is holding up perfectly in my jig setup, no signs of rust after repeated oil exposure. Thread engagement feels precise and smooth, and the hex socket drive grips tight without stripping. Exactly what I needed for heavy-duty tooling.

Had to torque these to 320 Nm on a press jig and the hex socket held perfectly without any rounding. The black oxide finish also resists rust better than the plain steel screws I used to buy.

Installed these on a heavy-duty fixture at work and the 12.9 alloy steel really holds torque without stripping. The black oxide finish is a nice touch for corrosion resistance too.