This is a drill guide for the Voron Berd Air Guide. https://thangs.com/kazolar/Berd-Air-mod-for-Voron-24-any-afterburner-compatible--36833?manualModelView=true
Use 3mm Thin walled tubing. I used this tubing -- 0.2mm wall
https://www.amazon.com/gp/product/B082FF8K22/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
You can use thicker wall tubing, but I haven't tested it. The tubing drill spacing, and number of holes impacts cooling performance significantly. I drilled each holed with a hand drill with a 1mm drill bit. Then enlarged each hole to 2mm with a 2mm drill. Crimp the short end shut and insert the long end into the fan/berd air assembly. The result produces the cleanest high speed PLA prints, and ABS enclosed prints which do not end up delaminating due to uneven cooling.