Quad Lock phone cases are excellent for everyday use, but they’re not 100% waterproof. One of these case-specific Poncho will help keep errant water and dust from being rammed into your phone it should be noted they're not hermetically sealed. Keep in mind Quad Lock was orignally intended for bicycle use. The Poncho will help keep out water and dust, especially if you're mounting the phone behind any kind of fairing.
In a submersion situation, or in the case of traveling through rain at highway speeds, only a true waterproof case like a LifeProof or Otterbox will keep your phone dry. These are still compatible with Quad Lock via the Universal 3M Adapter.
Note: Quad Lock phone cases and mounts are sold separately. Check out the Quad Lock brand page for details.