From The Truth About Guns:

For those who want all of the ergonomics, magazine capacity, ease of use, and affordability of shooting the AR-15 pattern rifle — and still remain compliant with California’s laws — the Kali Key is a solid alternative.

In essence, the Kali Key turns the semi-automatic AR-15 into a bolt action rifle. After installing the Kali Key, the rifle will only fire a single round with each trigger pull, and then requires the shooter manually operate the charging handle in order to eject and chamber the next round.