For quick and dirty vacuum sealing of frozen goods, one can just suck air out of the freezer bag. However, doing that directly by mouth is unsanitary. Hence this adapter.
Zip the bag almost shut, leaving just enough space for the eye-shaped part of the adapter. Press the bag around this part with your fingers. Breathe out, put lips on straw part, suck air out, then quickly remove adapter and shut bag.
I include three versions with different lengths of straw/tube. The one in the photo is a little too short for the pictured bag.
Print at 100% infill. I had some trouble with Slic3r leaving holes in the thin portion--the holes were obvious in the previous. Play with the layer width to solve this problem, or increase minimumWidth parameter in the Customizer.
This uses and bundles my Bezier library.