Blue Monster Teflon Tape
When details matter. This tape is thicker than cheap white PTFE tape. It's not stretched when manufactured, and is compatible for use on brass and stainless steel threading. The roll holds around 120' of tape, and you should always have some on hand for when things break or need to be assembled right the first time.
Stop buying the chap stuff. You will see the difference with this. Seals well.