This OEM modular cable is for "older version" of Seasonic semi-modular power supply 

models M12-500, M12-600, M12-700HM, M12II-520, and M12II-620.

By “semi-modular”, your power supply has two types of connectors only: 6pin and 5pin.

1) Two 6pin connectors: for 6pin to 6pin PCIe connector cable or 6pin to 6+2pin PCIe connector cable.

2) Up to six 5pin connectors: for 5pin to 3 x SATA connectors cable or 5pin to 3 x Molex connectors cable.

All other cables are built-in. For example: 24pin, 4pin and 8pin connector cables for your mainboard are built-in.