A lot depends upon the particular grommets used.
Tanks like the economy cartotanks sold by Valley View Vapors fit extremely tight on a carto, to the point that they are very difficult to perform
juice refills. Unless the tank is ordered with a fill screw, a blunt needle is required to refill with
juice, between the grommet and the carto. I found this to be extremely frustrating because the needle causes part of the gommet to be pulled into the tank with it, and requiring the grommet to be "teased" back into correct position with a tool like a dental pick. I ended up purchasing the accessory metal endcaps available onsite to correct this problem.



Economy Triple V pyrex grommet tank from Valley View, Triple V tank with grommets, same Triple V tank with traditional endcaps added.
However, the grommets used with the High Desert Vapes cartotanks don't fit so tightly on the carto. Snug enough to keep the tank from accidentaly falling off the PV, but allowing the tank to be easily slid up the carto for easy juice refills like other cartotanks.


High Desert Vapes pyrex grommet tank, High Desert silicone gommets.