You can see list of all pre-programmed devices using the command line version of K2pdfopt. I think letter "d" is for device selection, where you can see this list.
1. Kindle 1-5 (k2)
2. Kindle DX (dx)
3. Kindle Paperwhite (kpw)
4. Kindle Paperwhite 2 (kp2)
5. Kindle Paperwhite 3 (kp3)
6. Kindle Voyage/PW3+/Oasis (kv)
7. Kindle Oasis 2 (ko2)
8. Pocketbook Basic 2 (pb2)
9. Nook Simple Touch (nookst)
10. Kobo Touch (kbt)
11. Kobo Glo (kbg)
12. Kobo Glo HD (kghd)
13. Kobo Glo HD Full Screen (kghdfs)
14. Kobo Mini (kbm)
15. Kobo Aura (kba)
16. Kobo Aura HD (kbhd)
17. Kobo H2O (kbh2o)
18. Kobo H2O Full Screen (kbh2ofs)
19. Kobo Aura One (kao)
20. Kobo Clara HD (koc)
21. Kobo Forma (kof)
22. Kobo Libra H2O (kol)
23. Nexus 7 (nex7)
24. Other (specify width, height, etc.)
Hope this helps
