Paracord bracelets done in olive drab and black with side release buckles.  Tied with the cobra stitch and king cobra stitch, also known as the Solomon bar, Portuguese sinnet, square knotting, and macrame.

The larger one enables you to carry twice as much cord and is tied so that the outer layer may be untied and the inner bracelet remains intact.

To my knowledge, the 'cobra' knot name comes from gimp strap/plastic lace projects of tying the pattern to resemble a 'snake' bracelet, such as this example from the boondoggleman website.  I've seen folks mention that they were making the 'cobra' type bracelets back in the 1960's and '70's, but they're probably much older since the hobby/craft lace has been sold through such magazines as 'Popular Science' since the 1940's, and the knot pattern itself is older than dirt, with examples of the square knot found in Egyptian tombs.  So whatever you call it, just have fun tying it.

And just for fun, here's a link for an April 1940 story, from the Popular Science Archive, of a fellow using scrap parachute cord to make dog leashes.  ;)