The quality and plating and welds look really good.
Good instructions, fasteners, brackets + extra goodies.
I recently bought a NOS set of 4>1 for a GPz550.
The pipes were packed with yellowing California newspapers from May of 1980 when I opened the box.
Alphabet Headers had a great reputation and were well respected "back in the day" so I've been told.
Not much info about the company on the net though.