The ones that screw into the table replacing the VPI feet are the 1.5 1/4-20 thread ones. I suppose that you could use the unthreaded ones if they are the right height. You can use them either way but I have found that their cups improve the sound. In fact, their cups do a good job under standard VPI feet. At about $35 for 4 + shipping I think they are a worthwhile improvement , I use them under mine. I liked their products so well that I became a dealer for them, use their rack also. Their prices aren't cheap but they are not outrageous and they work just as they say they do. I don't mean to imply that there aren't other good products out there, these are the ones I am familiar with.