Eggestonworks Andria 1

If you take off the outside cone the screws underneath are 1/4-20. However you have to get long threaded rods 1 1/2" long. I have used 2"Audio Points, SS Stillpoints and now I am using AnCan Large size SS.
http://www.amcanaudio.com/?post_type=product

Thank you both for your reply will look into.
kel

K rose - One more option: no spikes but instead place your speakers on these:

http://www.audiopoints.com/Sistrum.php

I experienced an obvious and immediate improvement when I placed my Eggleston Fontaines (Andra's little brother) on these over their original spikes. Robert also has a newer and improved version, "Back-STAGE Platforms" if you wish.