AI2s (all in 2's) are a two part style of diaper. Instead of the absorbent fabric being sewn into a waterproof shell, you can remove the inner fabric so that it's a separate piece from the shell. When the diaper is soiled, remove the fabric insert and drop in your wetbag. The shell is then reusable with another clean insert, assuming it hasn't gotten dirty with the last use.
Example of a GroVia diaper - shell and removable/replaceable insert. Click to view larger.
Pros of AI2s:
very economical system of diapering
good for traveling and outings
no stuffing inserts - they lay or snap in
shell can be used with prefolds or other inserts
Cons of AI2s:
inserts take a long time to dry
can be bulky on small babies
shell doesn't always stay clean between uses
GroVia had a buy 3 shells get 1 free sale in April, so now I have 5 of the covers and 9 inserts so far. They fit Iris well, come in cute patterns and we've never had a leak. I like both the snaps and this particular velcro. I can easily pack extra shell and a couple of inserts in my purse and we're all set for an afternoon out. There are other brands available too. Definitely one of my favorites!