So I have a leak in my kitchen sink drain pipe coupling. My first thought was to simply unscrew the coupling and apply some new plumbers tape, however when I attempted to unscrew it I found that the bottom portion of tape was not applied to the coupling itself, and appears to be some kind of boot around the copper pipe instead. Does anyone know what it is?
Is it simply incorrectly applied plumbers tape?
Should I cut it away so that I can fully unscrew the coupling and apply plumbers tape to the actual joint or does it serve some other purpose??

the picture flipped upside down for some reason

>>2922347 (OP)
>Does anyone know what it is?
It looks like insulation.
You can probably cut it back some to allow the ring to drop more but just try loosen then tighten several times to see if it stops the leak.
That fitting may have a washer between the pieces instead of sealing tape or dope;

>>2922400
Ahhh I see, thank you very much
with this knowledge I can get this fixed myself today

Update: I cut away the insulation and applied a liberal amount of thread tape to the joint which did have some kind of washer
Success! No more leak
thanks again for the help

>>2922563
>did have some kind of washer
If it starts again, you should replace the washer.
Congrats on your success.