Thread type:	UNC
Head type:	Hex Allen
Drive:	Hex
Diameter:	1/4''
TPI:	20
Lenght:	1''
Art.No.:	ISH504081S
Material:	stainless steel A2

UNC thread (coarse thread) is used in materials like Aluminium, Zinc-Casting.
Beside all the usual screws with slot and phillips drive or pozidrive there are also screws with hex allen haed with UNC thread available. In german language these screws are called <INBUS>.
How this name became common, just have a look at WIKIPEDIA.

http://de.wikipedia.org/wiki/Inbus