At CWC we have some experience with airsoft grenades. Several members have owned the Tornado Timed grenade, but no one has ever ben fully satisfied with them. This year I added one of the Tornado Impact versions to my kit, and boy has it been fun.
I have yet to have a malfunction. The grenade detonates on impact, just as advertised. It's a surprise to your enemies on the field, and loads of fun to get a kill with.
For a quick overview of how they work, check out these videos.