Can I use an AGP 8x on my computer's AGP 4x slot for my video card?

I'm shopping for a new video card. My PC's motherboard has an AGP 4x slot. I see lots of video cards that say 4x / 8x, but some that only say 8x. I'm not sure if I can buy an 8x for my 4x slot. Also, if I can't buy an 8x for my slot, then what makes the 4x / 8x cards able to fit in both? Thanks.|||Maybe some 8x cards are designed to be able to clock down to 4x, some are not. Many times it will say whether or not this is possible right on the box. In all respects the motherboard or 8x card should not be damaged by attempting this, the worst that will happen is it wont work.