Here is what Fasna has to say:

If you want to fish more effectively near the bottom in a deep, powerful stream or river, the problem is often that one cannot reach the depth with ordinary brass beads. This problem is solved with a Tungsten bead. Tungsten is about 70% heavier than lead and more than twice the weight of copper. In addition, it is non-toxic, so it is kinder to the environment. This makes it possible to tie the flies nice and thin without applying extra reinforcements. By designing them Slotted instead of standard Conical (round) it is easier to use with any type of hook and hook bend.

2.0mm : 0.07 Gramm
2.5mm : 0.11 Gramm
3.0mm : 0.20 Gramm
3.5mm : 0.33 Gramm
4.0mm : 0.50 Gramm
4.6mm : 0.76 Gramm
5.5mm : 1.22 Gramm

Qty: 20 st.