We have a lot of zippers on our products here  and a lot of options for zippers.    A lot of times our patterns come with a pre-set selection, but we can customize more.  Locking, WaterTight and even air-tight zippers are sometimes requested as customization features.   You can always ask for a quote for something via the "I'd like to customize this product" link on any page.   Meanwhile, here's a simple picture to explain the type of zippers and what they are called.