I was given one of the new BD Magnetron HMS carabiners to test last November and have used it full time up until now. That represents six months of regular use at the climbing wall, several sporting climbing trips, UK trad climbing and alpine rock in Switzerland. I like simple, uncomplicated design which is why I have never been able to get on with any of the other auto-locking HMS carabiners. To me, there always seemed to be one too many twists or pull-backs to justify the extra security of the auto-lock gate. Over the years I tended to stick to a neat, compact HMS design with a conventional screw gate, such as the BD Pear Biner or Petzl Attaché 3D. One first impression I liked the sleek profile of the Magnetron. No bulky gate sleeve or folding plastic attachment. The extra spur coming off the base the the gate which creates a captive area for the harness loop means that the Magnetron does everything the DMM Belay Master does with no extra moving parts and, prevents dangerous cross loading of the carabiner. Remembering to get your belay loop in the right position (at the narrow end of the carabiner), takes a little practice and I got a bit frustrated by not getting it right for the first few days of use. What you need to remember is that every time you open the gate the belay loop is free within the full radius of the carabiner so you will need to correctly position the belay loop for each and every use. The same goes for the DMM Belay Master althought the Edelrid HMS Strike FG does have a sprung wire loop that stays in place regardless of the gate position. On balance I much prefer the BD system for simplicity. The Magnetron bit of the gate consists of two sprung, hinged flaps which snap into position over two imbedded magnetic inserts, in the hook of the carabiner. Again It's a really simple idea which will stand hours of fiddling when there's nothing better to do. There is something very satisfying about the way the flaps click into place and conversely release with just the right about of pressure from finger and thumb. Arguably the Magnetron system would be less likely to freeze up than a conventional screw gate but I haven't put that to the test as yet. I've certainly had no issue with grit fouling the locking mechanism which can be a problem with other auto-locking systems. I did take me some time to get used to the Black Diamond Magnetron Gridlock HMS and I very nearly switched back to a conventional screwgate at one point. Having used the Magnetron for several months now, I really like it and intend to stick with it. If you are looking for an auto-locking HMS the Black Diamond Magnetron Gridlock HMS is a very strong contender if not the best choice available. It is more expensive than it competitors but I think the clean, simple and effective design justifies the extra cost.