Beads are pretty much standard these days when tying trout or salmon patterns.  Wind River Outdoor Company carries a complete line of beads and at the top of that list is Firehole Stones! 

These round beads are composed of Tungsten and get your patterns deep and fast!  Available in 4 matte colors and 1 unfinished color in sizes (mm) 2.0, 2.5, 3.0, 3.5, and 4.0.  See the hook chart below if additional help is needed to find the size you need.  Tight lines!