The original from Fat Daddy direct from the USA.
Here the version 4 Low Profile, a special variation of the version 4 with not changeable and only 1mm thick top cap.
Different top cap sizes and options: 15mm, 22mm or 22mm flat top (without grooves).
As well as Version 4 (Regular) with O-rings and insulators resistant to heat up to 400° Celsius and integrated one-piece power connection.
Besides building your own mods also ideal for repairing and improving purchased battery packs.