HOLO-KROME 730001490 5/16-24 X 4" 內六角螺絲 | 六角驅動 | 合金鋼熱處理黑色氧化（50入）

The black oxide finish wiped clean easily and hasn't shown a hint of rust after a week in my damp shop. Drive engagement felt solid all the way down, no wobble even at full torque. Fifty pieces in that little box is a solid value for bench work.

These screws torqued down into my fixture base without any cam-out, and the 4-inch length gave me just enough reach through the spacer block. The black oxide finish is holding up better than the zinc-plated ones I used before.

These black oxide screws look clean and professional once installed. I used them to secure a jig fixture, and the hex socket drive made tightening a lot easier than a standard bolt. The 4-inch length was exactly what I needed.