Oil Drain Plug Size?

[spectaculous]

The Stahlbus drain valve is great. it make oil changes so easy and mess free. i like the fact that it comes with a short length of clear tubing. I've done several oil changes the normal way, with about a third of them making a huge mess. Thin oil and 8.5 quarts of it makes for some high velocity oil when you pull that drain plug out of the hole! With the Stahlbus, you just stick the tube into your used oil container and then press and turn the valve side into the installed drain valve and rest is cake. Well, almost. You still get to deal with an upside-down oil filter full of hot, dirty 0W-20! I wish there was a cleaner way to change the filter...