You can see that it is pretty small by comparing the length of the metal plate and the length of the card. Actual dimensions can be found on the Asus website: 120.9 x 99.1 x 21.6 ~ cm (LxWxH). However, I think they meant to write mm, not cm (a card that is larger than a square metre makes no sense). To see if it is compatible with your build, I recommend using PCPartPicker.com
The card is small, as per the above answer check PCPartPicker site. It should fit in a small factor box if it is the only card, depending on what your internal configuration is. The card is fast and reliable, I have it in the basement with the wireless router two floors above.