[Edit] This failed on me. The holes are too big and the PTFE expanded into the holes under filament pressure. Now I can't extract the filament or the tube. I'm still confident it would still work but with lots of much smaller holes. Next I may just stack TO-5 heatsinks on the tube. A buck each on ePray. [/EDIT]This thing is a modified MK5 / MK6 thermal barrier. The hole arrangement significantly reduces heat conduction / heat soak up the thermal barrier tube. This arrangement of staggered holes retains structural integrity that is otherwise lost with the horizontal cut-slit method. This solves or greatly reduces the problem of heat soak during long prints causing filament to soften and / or jam/expand in the PTFE. The thermal barrier dxf file is Makerbot's not mine.Use a fine Sharpie and make radial marks on your tube just above the insulation and kapton tape. Make another mark just below the flat barrier plate. Now make axial marks quartering the tube. Alignment isn't super critical but keeping close will help it look nice and get four holes with a fairly consistent web remaining. Clamp it horizontally in a vise. Also plan your cuts to cut towards the end, when those four are done, shift out and cut the next four, thus leaving the somewhat weakened piece not bearing any cutting load. I used a 3/16 end mill to plunge cut each hole. Rotate and cut the remaining 3 on that radius. Shift the thermal barrier tube out of the vise, clamp, index, and repeat. If you're doing this on a drill press rather than a mill you can use a rat tail file to file a flat spot to help prevent drill bit drifting when starting. When one use the back of a No 11 Xacto blade or your favorite deburring tool to debur the inside edge of the holes. Re-assemble your hot end and enjoy minimal heat soak above the thermal core.