The 15m Chrono is the size I haven't ridden. But I've had the 12m Chrono out a bit and found myself wondering if I'd ever use the 18m Chrono again. The 15m seems like a good compromise in absolute low end vs. turning speed. The 18m Chrono made me do stupid stuff like try riding in super light wind. It all worked great until I blew a tack and dumped the kite. The wind was so light I swam past the kite on my drift in, just dog paddling too.