Hex Key Selection Chart:

1.) Sizing :: Metric (Red) or Standard (Black)
2.) Singles Vs. Sets
Single Hex Keys	Hex Key Sets
3.) Length :: Short Vs. Long
4.) Regular End Vs. Ball End:
Regular End	Ball Point End (up to 30° angle)
5.) Finish:
You have 3 options for finish. Chrome finish offers extra protection and excelent detail. Rainbow/Colored finish offers fast identification of the tool along with the extra protection and excelent detail of chrome. Gold finish is a notch above the rest.
6.) Shortened Key w/ 100° Angle:
The special angle leaves enough space to grip with the hand.