Sawyer Water Bladders:
These are Sawyer's new 9 ply bags which are thicker and more durable that the originals. Great for water storage, and lighter and less expensive than comparable bladders. Caps are included, and since these have a standard thread pattern, if you lose a cap a regular soda bottle cap fits.
Three Pack of 1 Quart (32 ounce) Water Bladders (Sale - $4.95 per three pack!)