There is none. KR808, KR808D, 808, and Kr8 are various ways suppliers and vapers have used to abbreviate that tongue-
twister.
Caveats:
- Supplier LeCig distinguishes between KR808D-1 and KR808D-2. They use the latter term to refer to the E9 cartomizer-based model (e.g., Smoke51 DUO, Vapure, Green Smoke, Bloog, etc.). LeCig sells both models.
- Kanger, the manufacturer, has used KR-808 in its numbering of many different models, e.g.,
Most of which are not even cartomizer-based. There also are KR808G, KR808D-F, and KR808D-1P. [Considering that the spelling of the word 'design' was a challenge for them, I guess we should cut them some slack regarding their limited model-numbering vocabulary. They never met an 808 they didn't like.

However, for all practical purposes among vapers and suppliers, a Kr8 is a Kr8 is a Kr8 ... however it is abbreviated.