These printers use the SCX-4521D3 cartridge:

Samsung ML 1610

Samsung ML 1610 R

Samsung ML 1615

Samsung ML 1620

Samsung ML 1625

Samsung ML 1625 R

Samsung ML 2010 D3

Samsung ML 2010 P

Samsung ML 2010 PR

Samsung ML 2010 R

Samsung SCX 4321

Samsung SCX 4521

Samsung SCX 4521 FG

Samsung SCX 4521 F