These cartridges can easily be removed by simply pulling them straight out from the pen's aluminum body and replaced with a new one. Refillable cartridges contain pigment based ink that is waterproof and won't bleed or smear when used with Copic markers. Each refill contains 1 piece each. Use these cartridge refills in Copic Multi-liner Pens. For the black refill in pen sizes of 0.03, 0.05, and 0.01mm use ink "Cartridge A" (CREFLA), for all other sizes use ink "Cartridge B" (CREFLAB).