ZubitsMagnetic Shoe Closures Unisex 'Never Tie Laces Again' - Sizes 1, 2 & 3 in 12 ! Original 2.0!

Q: Do they come in pairs, as shown, for that price?

They come as a set of two. Enough for one pair of shoes.

Q: What happens to the rest of the shoelace? Is it tucked into shoe? Do you cut it off?

Your question is answered in two of the videos on this page. After installing the zubits, use the clips to slip over the laces and adjust for tightness. Then cut the rest of the lace off and tuck the ends in the side of your shoes. I do wonder though how much I am going to feel that little piece of plastic that holds the end of the cut lace. I'm sure it'd bother me.