Some cartridge needles have tighter membrane and some have softer and that varies from brant to brand and you have to kind of guess when you first time buying new brand cartridges. Now Inkclaw have made it as option and you have options on soft, medium and hard tension on membrane that would work better on different types of machines and probably on personal preferences on some tattooists.
EZ Tattoo
EZ P5TS Tattoo Pen
