Like its bigger brother the KNS 6400s come in a very colorful cardboard box.
KRK Systems use almost the same bundle for the 6400 as they did on the 8400, except for the omission of the add-on cable with in-line volume control. With each set of KNS 6400 you get: microfiber cloth, carrying bag, and a manual.
The KNS 6400s look almost exactly like their bigger brother. The only visible change beside the pad material is the badge area that has been re-designed.
KRK Systems' use of bayonet type connectors for the headphone end of their cables is a nice detail. It works flawlessly and allows the user to change the cable if damaged. Unfortunately KRK Systems have not yet released any short or special cables. If they ever released a shorter cable with a microphone on it I am sure it would become a massive hit.
Even though the headband has two distinct pressure points they are never uncomfortable, not even for abnormally long listening sessions on a normal sized head. Like all closed back headphones you do get slightly hot ears, however, KRK Systems are quite good in this regard compared to other closed back headphones.
Another great feature of the KRK Systems headphones is how rugged the design is, and even though they are not quite in Aiaiai territory they are definitely close with their heavy-duty plastic enclosed headband and adjuster system.
One of the things that make the KNS 6400 cheaper than the KNS 8400 is the use of less expensive traditional pads. While not uncomfortable or ill performing they are simply not as well performing as the memory foam type pads used on the KNS 8400.