If you are flaring the "ferrule" or sleeve is immaterial and they are interchangeable. More important is the tubing. Do not use seamless stainless tubing
for flaring. If you look down the barrel of your tubing and the inside diameter is not centered in the tubing it is seamless and will not flare properly and it will leak.
Welded and drawn stainless tubing is not easy to find these days.

If you are using a compression style fitting welded and drawn tubing and seamless are interchangeable.