I'm already a pic ahead than with my description. Get your hole saw kit out and your pocket knife. If you don't have a hole saw kit, use a jagged edged insulator. Make the indent in the bottom foam to match the CD # your shipping. I used a CD 106 jagged edged Hemi 9 to make the first cuts. Then I used a jagged edged CD 121 or CD 122 to make the second cut. I found it worked best to use both of those sizes when making the rings that the insulator fit in. Use a jagged style to cut molds that doesn't have a petticoat, threads, or thick glass that makes it hard to cut. Some of the hemi 9s have threads that start up close to where the wire groove is. I shipped a bunch of CD 121s and then changed the size of cutting tool to fit some CD 106s, CD 126s, CD 143s, and a couple other different sizes.