Sand grains can get into the nozzle of your PORTALO and keep it from closing properly after use.
With this filter, the problem is gone!
It sits at the end of the tube inside the bottle and stops sand and larger particles before they can reach the nozzle.
Portalo is designed for clean fresh water. This filter is here for the moments when your water source isn't perfect.
Please note : It filters particles only. It does not purify or disinfect water.
Using seawater occasionally? Just rinse Portalo with fresh water afterwards to keep it in good shape.