Its here. The actual hole for the mflb though is 1/4 in, so if you want the tube to go directly in the hole you should get a 1/4 in Outer Diameter and some other inner diameter. The one I have fits around a stem and is a 1/4 in Inner Diameter and a 3/8 in Outer Diameter. It's safe, you just are forced to buy more than you will ever need.