My 2nd PC i bought only has PCIE X1 slots, i tried the zotac graphic card from Amazon but it was'nt a much of an upgrade for games than my onboard graphics. Purchased this and did'nt think it would allow my PCIE X16 card to play much, how wrong. Dont know how but this adaptor gives my between X4 and X8 speeds through my PCIE X1 slot even playing Crysis on High settings. If you only have X1 slots get this and a PCIE x16 low profile card its amazing!