Purchase Options:

Set of 4 = One 5L, One 10L, One 20L, & One 40L Dry Bag
5 Liters = One 5L Dry Bag (Black)
10 Liters = One 10L Dry Bag (Yellow)
20 Liters = One 20L Dry Bag (Blue)
40 Liters = One 40L Dry Bag (Orange)

Features:

Keeps Your Gear Bone-Dry: Special polyester interwoven with special waterproof fibers keeps even the tiniest drop of water out, so your gear stays dry and in perfect condition.
Simple 3-Step Waterproofing: It's super easy to waterproof your gear. Just place your gear inside the bag, roll the top down several times and snap the buckle closed. That's it! Your gear is completely protected from water damage.
Plenty of Storage: The medium Dry Bag has 20 liters of space, and the large Dry Bag has 40 liters of space, which is plenty of room for all your electronics and most valuable survival gear. 
NOTE: the “medium” bag is miss labeled as “small” on the package, but don’t worry its plenty big!
Easy to Carry: The roll-up top doubles as a comfortable and sturdy carrying handle. This makes it easy to grab and go in a hurry. 
Saves Space: Even the 40-liter bag stuffs down to the size of your fist, so it's super easy to store when not in use.
Won't Rip or Tear: The special polyester material that makes up the Lightweight Dry Bag is tightly woven together to stand up to all kinds of abuse. You can depend on it to keep your expensive gear safe from water even if you’re rough with it.
It Floats: trap some extra air inside your dry bag and it can float. Up to 10 pounds of your heavy gear will float safely. 

Specs:

Capacity: 5L (Extra Small), 10L (Small), 20L (Medium), 40L (Large)
Weight: 1.6 oz. (Extra Small), 2.2 oz. (Small), 2.3 oz. (Medium), 3.9 oz. (Large)
Material: 210T Terylene (Waterproof polyester)
Length: 13.5 "inches (Extra Small), 15.5" inches (Small), 18" inches (Medium), 23" inches (Large)
Width: 9" inches (Extra Small), 13" inches (Small), 15" inches (Medium), 20" inches (Large)