I'm a Live Audio engineer and bought these to use with some M20 K&M distance poles. They do a better job than my previous Adam Hall M20 sockets and were a closer fit.
I fitted these to a pair of Alto Black 18 subs, however, they didn't line-up perfectly. I'm not sure if this is due to the Alto's not being a standard fitting or the sockets not being quite right for a universal fitting. They needed slightly bigger holes drilling into the sockets (1mm) in order for the bolts to line up with the threads on the subs. They also could have had a larger diameter in order to spread the load more as they were smaller than the recessed area on the subs.
However, like I say, I'm not sure whether this is a problem with these sockets or with the Alto subs and so it would be unfair to mark them down without knowing for sure.
I may eventually secure them further to the M10 rigging points on the subs for more stability. But all in all... Another good product from K&M!
The K & M 24116 is a fantastic purchase, possibly the best our band has ever made. Our old speaker stand just sat into the mount, and the top would often shake, or if people knocked into the bass bin then the top would look like it was going to fall sometimes, also taking the speaker off the stand was awkward sometimes. With the purchase of this speaker mount we don't need to worry about that any more, everything stays steady and the speakers are easy to take off the pole