There could be a leprechaun and a pot of gold hiding underneath our kitchen sink, and we'd never know it, given all the things balanced precariously around the drain pipe under there. Which is why we love the idea of these adjustable shelves. The shelves slide back and forth, so you can click them into place around the pipe or garbage disposal, using as many or as few as you need. They make more of the under-sink area usable space, since you aren't limited to setting things on the bottom of the cabinet.
And if you have a few tall bottles, you can move the upper shelves to make room for them. That's harder to do with a regular, fixed shelf.