Welding Tips and Tricks

Has anyone tried this cup? Why does it exist? I accidentally got one to use with a standard gas lens for my 3-series (17) torch, thinking it would be a bit smaller than the 3AG12. It looks like it's made for a stubby, but the threads don't match. What's it for?

Looks like it's for a regular (medium) gas lens setup. Gotta be careful when the cup orifice is larger than the diameter of the gas lens. People usually get the best results with a diffuser, since the the diameter of the medium gas lens is 0.5" (#8).