The name is self explanatory, a piece of plastic that blows up when you throw it, but it has a special feature. It has a pin that actually prevents it from blowing up from things like accidental drops or anything of that nature. Once the pin is out, it is very sensitive and will blow up if dropped from about 2 feet above the ground. (The pin will not save it from throws though. If you THROW it with the pin in, it will blow up.)
I give credit to Darth Tso and Fred Da Bunny for the idea of the pin and the design. Thanks guys!
Step 1: Building the grenade
Step 3: Rubber bands.
Once the rubber bands are on, you can take the pin out to throw it, but if you aren't throwing it, keep the pin in so it won't blow up accidentally.