I heard an adapter IS needed to provide the air inlets for the KR8 cartos
901 to 808 adapter (or it may say 901 to KR808D-1 adapter)
It may depend on what cartos you have. The Vapor4Life KR8
batteries have a deep groove
through the center of the battery central post to provide airflow to their cartos. The 901 battery might not.
Note - the 901 atty needs no adapter to be used on KR8
batteries because the atty has its own air inlet hole