Not just aftermarket - my new model 19 Classic stocks have two pins in addition to a hole for the stock pin, one under the rear curve of the trigger guard, and one at the bottom of the target style stocks, underneath the bottom of the grip frame. And baby, they're very loosely fitted in their holes!

Are they needed? I don't know, I'm no engineer. But they came with it, so I like to have them in place. And I doubt makers are spending any money on something that isn't needed.

I replaced the factory stocks with Nills, and their pins are tighter than two coats of paint.