ZB-24: #236-242-Dual: Fits All 1200 Series (Except #1256-1257-1258-1268) & Models #502, 504, 510, 521, 604, 621, 704, & 721. Price $39.95 (also know as TK24 Cartridge Mount. Note: 2 ZB24's are pictured, you are only purchasing 1 (one) ZB24. This is only the cartridge mount. If you also need a cartridge you will need to go to the cartridges section and purchase one. If you are purchasing a cartridge we can install on headshell if you select the Install Pro. Option.