KR808D-2 (aka Chinese wholesaler model E9) exists with rip-off rebranders and I think AZSmokeFree
It is incompatible with and less popular than KR808D-1
KR808D-1 has the vendors with reasonable prices, the adapters for other models' attys, the fat battery version (CigEasy's Elegant Easy), etc.
KR808D-2 mostly has the ripoff rebranders who charge $40-50 for a battery, claim a carto lasts as long as a pack of cigarettes, sell cartos with hard or hard glued caps to discourage refilling. Those companies are not allowed on this forum.
AzSmokeFree, as part of its business, provides a more economical source of spares and cartos for people who already have the "named" rebrander KR808D-2 models