One unit is included.
The Strike Industries ISO-Tab for Strike Latchless Charging Handle with tabs installed on both sides add about 0.5" of length on each side of the charging handle.
Yes, this should be compatible.
Yes, this should be compatible.
One unit is one tab in the packaging. If you want to have both sides of your Phantom Charging handle extended then you’ll need to purchase 2 like I did. Hope this helps and clears things up for you.