I think that means that the adaptor will fit a 808 (Halo) or 901 (no idea what that is) battery so you can attach a 501 topper. I've got adaptors coming out of my ears, and none of them seem to be any good for anything LOL
I've been trying to figure out exactly what type of threading the Halo Triton battery has. I've been coming across KR808d-1 a lot, and I've been trying to find an 808d-1 to ego adapter to no avail. I've also seen 901/808d-1 to 510, etc. Can anyone clarify this?