The Scientific recycler, also called Klein recycler which is essentially a combination of the inner and outer recyclers. They constitute of two different tubes – one for intake and one for drainage. This ensures that they don't interfere with each other and act totally independently, providing filtration and percolation at the same time, but in different parts of the bong. This allows for maximum smoothness and efficiency. The scientific recycler is widely regarded as being "insanely cool". This is the best kind of recycler bongs, Ultimately it always make by the craftsman who has more than 10 years experienced of glass blowing. Even it cost more for these recycler bongs , but I ensure that it's a perfect gift for stoners.