Purilens keeps a simple product simple. PuriLens Plus is a buffered, preservative free saline that has been on the market for more than fifteen years, and it is pH balanced to sit close to natural tears.
Saline rinses, and it fills. Scleral lens wearers fill the bowl of the lens with it before insertion. Rigid and soft lens wearers use it to rinse a lens after cleaning. What saline does not do is disinfect, so it never replaces the cleaning and disinfecting solution in a routine. Keeping that distinction straight is the single most useful thing to know about it.
PuriLens Plus comes in more than one bottle size and in multi bottle packs, including sizes that clear the carry on liquid limit for air travel. Buying by the pack usually works out cheaper per ounce, and preservative free saline gets used generously, so wearers tend to go through more of it than they first expect.
Filling and rinsing routines differ from one fit to the next, and the solution you were given at the fitting was chosen for your lenses. Your eye care professional is the right person to ask before you change any part of that routine, including the saline. It is also worth checking the label on the pack you have at home, because saline, rinsing solution and multi purpose solution look alike on a shelf and are not the same thing.