M4-0.7 X 5mm 六角穴付きキャップスクリュー | フラットヘッド六角穴付き | 全ねじ | クラス12.9 合金鋼 熱処理黒色酸化被膜 (400本/パック)

The hex socket drive seats perfectly on my Allen key with zero wobble, and the 12.9 alloy steel feels rock-solid when torqued down. I've used about 50 of them so far on a jig build and not one stripped or rounded out, which is rare at this size.

The black oxide finish is exactly why I grabbed these for a tooling fixture—they slide into the hex socket cleanly and don't fight my driver, plus the 12.9 grade gives me confidence they won't strip under load. For a 400-pack at this price, I've got enough spares to last years.

Installed a dozen of these in a jig I’m building, and the hex socket drive makes tightening them in tight corners so much easier. The black oxide finish gives a nice, uniform look without any sharp burrs.