Bead Heads that are specifically drilled to fit over tyer's tubes.
The Medium Beads....7/32" fit perfectly over 3/32" OD tubing. HMH and Eumer cut-your-own small size in particular.
The Small Beads....3/16" fit perfectly on HMH Micro Tubing which is used for nesting inside other tubes. The Micro is also used as liner tubing on the European style tubes as well as the Copper and Aluminum tubes from HMH.
They are available in brass, nickel and black. 10 per package.
HMH Bead Heads for Tube Flies