Guru bead - the big, three hole bead for making mala necklaces and similar. The big bead has a large T shaped hole - out each side and the bottom of the bead. It can be a bit of a puzzler to figure out how to get the thread through the bead. These two video show two methods and make it really clear. They are really short too. Method 1 - Down and Back Method 2 - in from both sides . The guru bead is about 12 mm across, and the cap, tower or smaller bead is about 12 mm long.

12mm Hole size is approx. 1.2mm. By the each.