I believ it's an Allen Wrench. This is what Ernst says:

Inbus-Schraube (Markenname) s. Innensechskantschraube - hexagon socket screw, Allen screw

HTH,

Antje

I found this under "Imbus-Schluessel", rather than Inbusschluessel. But the same dictionary also has Inbusschraube, hollow screw. So I think you're OK with this translation.

the hexagon shaped key

Allen key der Inbusschlüssel
allen wrench der Inbusschlüssel
hex-wrench der Inbusschlüssel

Good luck !

:-) Damian

"Allen key" (BE) or "Allen wrench" (AE)

The use of "hex-wrench" could be confusing because thousands of different wrenches have hex heads.

Here is the content of an old KudoZ question on the same subject:

Inbusschlüssel
Translation
"Allen key" (BE) or "Allen wrench" (AE).

Asker:André Lotter
Jan 25

[by mccrosky] Jan 25
Answer: Allen key (BE) or Allen wrench (AE)

Explanation:
An "Imbusschlüssel" is another name for
Innensechskantschlüssel which is "Allen key (BE) or Allan wrench (AE) - Ernst – Wörterbuch der industriellen Technik

There is a mistake in my edition of the English > German volume of Ernst – Wörterbuch der industriellen Technik. "Allan key" or "Allan wrench" as written in Ernst English > German, but it hould be "Allen key" (BE) or "Allen wrench" (AE). Uel has the correct spelling above. Not only the German > English volume of Ernst – Wörterbuch der industriellen Technik but more importantly NODE – The New Oxford Dictionary of English confirms the spelling with "e".

HTH - Dan

[by A.S.] Jan 25
Answer: Imbusscluessel=

Explanation:
= hexagon socket spanner
References:

Hueber/technik

[by uel] Jan 25
Answer: Allen wrench

Explanation:
An Inbusschlüssel (note spelling) is an Allen wrench.
[Ernst, WB Ind. Technik]

References:

Ernst, WB industrielle Technik

HTH - Dan