Those beads used by me are from Troutline . But I'm sure that you can find in USA in different store. The design ( shape) of these beads was developed by french business Bidoz a few good years ago. As you know, the main source of tungsten is China. These beads now are copied by chinese factories and they sold everywhere. Different sellers like Troutline, Hareline and so on have these beads colored in different ways.
here is photo with those from Europe:
Pros for these beads:
* you can use in thorax area with nice effect and more balanced behavior
*you can give an eccentric effect on normal hooks something similar with jig hooks ( especially where jig hooks are banned ), the fly will "swim" with point up ->less snags
*more expensive than classic tungsten or slotted tungsten beads
*not so comfortable in tying, you need a lot of thread to be fixed on the hook shank
I hope it helps