60 ml syringe is very helpfull in refilling cartridges with capacities higher than 20 ml. It makes refilling easier and faster, because it is possible to fill the cartridges like HP 15/45, HP 10, HP 88 with the ink with one apply of the syringe.
60 ml syringe is recommended also to remove the rest of old OEM ink from cartridges, because of higher than in 20 ml syringes pressure.