M6-1 X 25mm 內六角圓柱頭螺絲 | 半圓頭內六角驅動 | 全牙 | 10.9級合金鋼熱處理黑色氧化（600/包）

These bolts came perfectly threaded and the black oxide finish looks tough. They seated flush in my jig without any wobble, exactly what I needed for a secure hold.

Grabbed a pack for a jig I’m building, and the hex socket engaged perfectly without stripping, unlike cheaper cap screws I’ve used. The thermal black oxide finish seems durable enough to handle clamping pressure.

The black oxide finish on these M6-1 screws is tough and consistent across all 600 pieces, which saved me time sorting for a tooling fixture. They threaded smoothly into tapped holes without binding. A solid buy for the quantity, just wish they came with a few extras in case one gets dropped.