I own a set. They could be constructed by a competent seamstress. Basically, a piece of waterproof, canvas-like material, sewn into a tube shape, with various sized silkscreen sewn into one end, to act as a 'filter'. No "secret" that I know of. Even the size mesh(silkscreen) used for the screens, is available on the site, I believe. http://www.informationon.com/bubble-hash-hashish/index.html