I use Boge cartos xl sr punched. I use a 20 gauge sharp needle as the filling is tight and very hard to get a blunt needle down the sides. I fill with 1.5 to 1.7 ml of
juice. Half of it in one side pushed down as far as I can and slowly raise trying to fill the whole carto repeat and put the other half on the other side of the carto. I Iusually have to blow a tiny bit of
juice out of the center post then I'm ready to insert the carto in the tank, fill and vape with no problems. This method had never failed me for over six months.