When the factory hose on my K3 disintegrated, I replaced it with standard 4 inch flex hose. After about an hour of struggle and swearing, I finally got it done but it was a big PITA. It proved essentially impossible to preform the end of the wire reinforced hose accurately to the shape of the dust shroud, the hose circumference was barely sufficient and access was extremely limited and awkward. If I had it to do over, I would spent the time to fabricate an adapter, rather than fight with getting the flex hose to do something it was never meant to do. The 3D printed solutions others are recommending sound ideal. But I can imagine making an adapter that consists of a plywood fabrication to mate with the dust shroud, attached to a standard male coupler to connect with the flex.
It really is ridiculous that the K3 doesn't have an adapter to make this connection and Felder uses such cheap flimsy hose.
