HOLO-KROME 33100 5/16-24 X 3/4" 杯頭內六角止付螺絲 | 合金鋼 熱處理黑氧化 (100入/包)

Installed these on a gear hub and the cup point bit into the shaft perfectly for a solid hold. The black oxide finish doesn't flake off during tightening like some cheaper set screws I've used.

Grabbed a pack for a shaft-collar assembly job and the hex socket drive seated perfectly every time, no stripped heads. The cup point bit into the shaft just enough to hold firm under vibration. One hundred in the box means I won't be reordering for a while.

The black oxide finish is really consistent across all 100 screws, which made assembly look clean and professional. They torqued down nicely in the tapped holes without any binding, exactly what I needed for securing a small pulley assembly.