'Double Zip' adds a new dimension to pumping! The double zipper allows you to decide which side tubing will extend from.Standard size Pump cases measure approx. 2 1/2 inches wide by 3 inches high. They hold all pumps except for the distronic d-tron pump which is larger than standard size pumps. D-Tron Size is also available in this style. Splash Paks are water resistant which means that water will bead up on the pak and they will dry out quickly, great to use with water proof pumps or for a day at the amusement park where water rides may get you wet. These are not water proof due to the stitching and zipper.