Kingstyn's new valve design has no cap. Other bags rely upon a cap to be tightly sealed to keep air out but air can still seep through the cap causing the bag to deflate over time. Kingstyn's new technology in our no-cap valve created an airtight harrier keeping items condensed for the long haul. If you do not have a vacuum handy you can compress bags by simply hand-rolling the bag to remove excess air. Increase storage space in your suitcase, luggage, or closet.