Get a waterproof moto backpack and a back protector separately.

You don’t need a backpack with built-in back armor; a separate back protector and a solid waterproof bag is the smarter, cheaper, and more comfortable commuting setup.

Integrated armor backpacks sound convenient, but they’re usually a compromise. The armor is fixed in place, often too short, and you can’t adjust it to your body. A separate back protector insert (like the Level 2 inserts from D3O or Forcefield) can be slipped into a backpack’s internal sleeve or hydration pocket, so it sits exactly where your spine needs it. That’s better protection than most “armored” backpacks give you.

For the bag itself, look for a roll-top or welded-seam waterproof backpack from a motorcycle-specific brand. Kriega makes excellent ones — the R20 or US-20 are popular for commuting because they’re genuinely waterproof, don’t flap around at speed, and have a pocket that happily holds a back protector. Mosko Moto’s Moto Rackless Reckoning is more spendy but bombproof if you want something that’ll outlive your bike. The key is that the backpack cinches tight to your body, so the weight stays on your shoulders and hips, not bouncing off your lower back.

If you absolutely insist on one piece of gear, the Alpinestars Evac WP does have a decent integrated board and a roll-top closure, but it’s heavy and hot in summer. You’ll be better off with the separate setup — it’s more flexible, easier to wash, and you can wear the back protector off the bike too.

Your back will thank you after a five-hour ride in the rain.