It will use an x16 slot physically (though no consumer board I've seen has a PCIe slot physically limited to x8 anyway, just x16 slots which may under some cases run as x8). After that, it won't matter too much for this card; as it isn't a super high end card the difference between x16 and x8 won't be significant (especially with PCIe 3.0). As to whether it's a "good" card, it depends on what games you're trying to play at what resolution, and how demanding a gamer you are in terms of settings and performance. Offhand it seems good for the price, though as with all parts you could get more performance for more money.