I googled these just now, and note that somebody(s) had a problem with Ciener. years ago, I noticed his arrogance at a gun show and on the phone. However, nobody else is offering these very useful items, so I suggest that you get them thru some outfit like Midway, so that you have some recourse if there's a problem with your unit. I've owned 1/2 dozen of them over the years. Some needed a bit of fluff and buff smithing work, some did not. Given the very wide range of guns in which these units are expected to function, the need for a bit of tuning is to be expected. However, if the man and the company are getting stupid about their customer-satisfaction, somebody else should take over the marketing of these units. The AR unit, for sure, has been available far longer than any patent protection is available.