The Patriot Pin is a clever method to make California AR-15s compliant. You simply replace your receiver endcap with theirs and the rear takedown pin. Unlike other similar designs, Patriot Pin uses delrin for their takedown pins. Delrin is a self lubricating material so it makes it easy to open and close into the receivers. This helps maintain the life of your AR.
Their takedown pin is actually ramped and does not have the detent hole. The pin is still captive but it is designed to be easy to reinsert without getting hung up on the detent.
The Patriot Pin only requires the shooter to use his or her thumb to pull the takedown pin out and you can simultaneously remove the magazine.
Due to California law, a fixed magazine can be removed if the gun is disassembled. Opening the upper receiver satisfies this and Patriot Pin’s magazine release can now be pressed to release the magazine.
They have come out with a Patriot Pin 2.0 which will incorporate a QD sling hole.
For people who do not want to use the Patriot Pin, they are making the Delta Pin. It features an easy pull tab that folds flat when not in use and indexes 90 degrees to the receiver. It is like a giant extended take down pin. Just like the Patriot Pin, the Delta Pin features a delrin pin. They will also be releasing a front delrin pin. If you think about how often you will need to open your AR-15 for reloads, the pins will take a considerable amount of use. Delrin will be easier on the receivers both in terms of less friction and abuse.
Here is a handy flowchart for those living or moving to California to know if your semi-auto is assualty or not.