I have no idea. I bought 'em for $16 shipped from a member (The Dali). I modified them by getting rid of the front potion of the clamp and carefully placed some holes in the back clamp to allow screws to attach the speaker.
I liked your mounts because of the side clamp action but it was tough for me to cough up $80 at the time to mount $50 speakers. AH to the rescue!
"Honey, but they're only $10. Please give me my balls back!"