Based on http://www.thingiverse.com/thing:695226, this adapter fits K40-style 40W chinese laser cutters for connecting a 4" exhaust hose.
Improvements include:
Like the original, the two-part version is joined by two 3mm bolts.
Fan_Adapter_v2.SLDPRT | 532.5KB | |
Fan_Adapter_v2.STL | 1.2MB | |
Fan_Adapter_v2_split.STL | 775.5KB |