It has a lifetime warranty, a flexible boom, dual volume controls, mono/stereo, and appears to be ruggedly built

The headset that was shipped to me does have the flexible mic boom

In either case, I received the HS-1A with flexible boom.

I believe the difference is that the HS-1A features the flexible boom where the HS-1 may not.

Was delivered as shown with the flexible mike boom

The headset I received is in fact the "HS-1a" which is what is pictured (it has the flexible mic boom)