Allen Wrench Size

allen wrench
An L-shaped metal bar with a hexagonal head at each end, used to turn bolts and screws having hexagonal sockets
a wrench for Allen screws
A hex head wrench
A hex key (also known by various synonyms) is a tool of hexagonal cross-section used to drive bolts and screws that have a hexagonal socket in the head (internal-wrenching hexagon drive).

size
Extensive dimensions or magnitude
(used in combination) sized; "the economy-size package"; "average-size house"
cover or stiffen or glaze a porous material with size or sizing (a glutinous substance)
the physical magnitude of something (how big it is); "a wolf is about the size of a large dog"
The relative extent of something; a thing's overall dimensions or magnitude; how big something is
Each of the classes, typically numbered, into which garments or other articles are divided according to how large they are