2-15-17 This funnel will thread into flask heads, but it is very tight and I suspect it is out of spec. I tried it on 4 different flasks with the same results. I purchased it to replace a similar one that had become lost. The old one fit much better than this.
The cone and the tube of this funnel are separate pieces that are soldered together. On my example the soldering was poorly done with smears up the side of the cone.
Overall, this piece is functional but not of the quality I expected.