I was a firm thumbreak believer... and still am - nothing else is as efficient as a thumbreak when trying to keep a gun inside the holster - all I gotta do is be actively trying to keep it there.
But I just bought a Blackhawck CQC hoster with Serpa rention and, with a slight adjustment of hand position, it works just about as well...
So I'll still register as a thumbreak fan, but I do recognize there are fine quality holsters out there that'll do a very acceptable job too.
