This page gives installation advice about installation of Speaker spikes with Anchor Nut
1) If you click on the picture of the product and get the larger image, you’ll see it has an anchor nut that requires about an 8.5mm hole, 9mm deep.
2) We recommend drilling the hole, installing the anchor nut using a hammer to tap it in.
3) Then carefully removing the anchor nut and re-installing with PVA wood glue.
Step 2) and 3) are particularly required when installing into Floor Standing speakers.
If you are installing into metal stands then you can drop the anchor nut, but require a metric M6 thread, 10mm deep.
The spike section of NX-SF-003 & 004 is 18mm high, and the spike section of NX-SF-011 & 012 is 34mm high. Both are 13mm Dia at the top of the spike and come with Feet which are 18mm Dia.