I've spent a couple of weeks trying it out on steel string and a tele. Works well for both, although you have to like the metallic tone. The fitting system works very well, with a high degree of adjustability, and it stays very, very firm and stable on your thumb without feeling like it's pinching, as many of these do. Overall, I'm pretty impressed, although I'm not an expert with the thumb-pick (string muting is more difficult).