Obviously, Blue Tac is a name brand. I never used the stuff. What I used, and recommended to Warpdrv was a similar material I picked up at a local hobby store (you know... the girly ones). Think of it as a sticky putty. It never seemed to dry out, and if left alone, forms the perfect bond to hold speakers onto stands. It is more to secure the speaker form falling off the stand if bumped or knocked over. However, once knocked over, the speaker will peal off the material.
If I was ever to run speakers that required stands again, I wouldn't hesitate to use this type of material again. I used it for about 4-5 years with my last sets of speakers.
