The GPU-oriented PCI Express 4-Way Flexible Splitter was designed to expand your modern motherboard (ATX, mini ATX, etc.) with up to four x16 PCIe boards, such as GPUs. The splitter’s host board goes into just one of your motherboard’s x4 / x8 / x16 PCI Express slots.
The GPU-Oriented x1 PCI Express 3-Way Splitter was designed to expand your modern motherboard (ATX, mini ATX, etc.) with limited PCI Express slots. It allows you to connect up to three x16 PCI Express add-in boards, such as GPUs, to your motherboard’s x1/x4/x8/x16 PCI Express connector.