Depends on which size autosiphon you have. I have the 1/2" version which fites 1/2" tubing just fine. The one I had before was a little loose with 3/8" tubing so you may want to go with 5/16" (Just run it under hot water first to make it stretch easier)
I currently use 3/8" silicone tubing on my 1/2" racking cane, stretches over it nicely. I'll order some 1/2" silicone someday maybe, would make transfer faster.
"People should not be afraid of their governments. Governments should be afraid of their people." - V
Secondary: Shady Lord RIS, Water to Barleywine, Pumpkin wine, burnt mead
Kegged: Crappy infected mild
Bottles: Apfelwein, 999 Barleywine, Oatmeal Stout, Robust Porter, Robust smoked porter, Simcoe Smash