I've seen these advertised for years but have not spoken to anyone who has used one. The ATF suggested that even David Koresh used them, if ATF says I doubt.
Same with me. I've seen them advertized for years, but have no personal experience with them, & I've never met anyone who has. However, since they've been advertized for years, somebody must be buying them. Hopefully somebody on the site knows something about them and will share with us.