M20-2.5 x 30mm 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（25個/包）

The black oxide finish held up perfectly when I used these to mount a precision assembly fixture—no rust at all after a month in a humid shop. The hex socket drive seated cleanly without stripping, and the Class 12.9 steel gives me confidence they won't shear under heavy loads.

Used a set to secure a heavy-duty jig on my mill, and the Class 12.9 strength handled the torque without any stretch. The hex socket drive seated perfectly with my Allen key, and the black oxide coating seems to resist light oil stains well.

The black oxide finish on these M20 bolts is exactly what my fixture assembly needed—uniform and tough-looking. The 12.9 alloy steel feels rock solid when torqued down, and the hex socket drive seats perfectly without any wobble. A full day of machining and they haven’t budged a millimeter.