I bought two pair, but one package contained enough laces for both my shoes.  I wear a size 7, the shoes were low rise Converses, and I used the standard lacing pattern.  The company is pretty excellent in sending you a supplemental email with a tutorial video link.  I watched the video about four times before attempting to try it (I didn't want to accidentally cut the wrong length of lace and have to re-order), and it was very easy to install the little clamps and lace up.

I love how my Converses look with these new elastic laces. They are super easy to take on and off, which is a god-send considering I visit a lot of my Asian friends who have a no-shoe requirement in their homes.  Before these laces, I had to sit down to untie my laces; now I can just slip them on and off and keep going.

I find the little clamps at the beginning and end of your shoes to be barely noticeable.  Sometimes, the clamp near my toes feels uncomfortable, but that's usually because it gets turned around or smooshed farther down than normal; I just slide it back to the right position and I'm good to go.