Without a mesh bag fitted to an inspection port, gear can move around inside your kayak. But, fit a mesh bag and things will stay right where you left them. And, it is easily removable should you ever need to reach inside your kayak.
This is designed to work with Oceans inspection ports. It may work with other brands, but they need to have the right size and shape opening to allow the bag to fit in place. Use a 5" bag with a 5" hatch and a 6" bag with a 6" hatch.