I saw on Holosun's Facebook page that they were giving away one of their sights. I entered and won. When I asked, they were kind enough to substitute me the 30mm version of the one that was up for grabs. So I've got a HS502c on it's way to me, free of charge. BTW. Holosun is the OEM that makes the Primary Arms sights. I figured I'd give them a plug for hooking me up.
http://www.holosun.com/store/index.php?route=product/product&path=64&product_id=86
http://www.holosun.com/store/index.php?route=product/product&path=64&product_id=86