It’s a jig-style pattern, so it’ll ride up-side-down, and therefore not snagging on the bottom that much. Next to the “Simon Templer nymph” and “La Bomba” it has become my go-to fly for fast water. It’s a real killer! The CDC gives this fly something special under water.
Also try some more color variations. Same fly, but with an olive abdomen has given me great results for grayling. You can fish it in a team of flies, as a point fly or middle dropper, but you can also fish it as a single fly. In Slovenia you have this fly as a single, because it is not allowed to fish with multiple flies.
I’ve fished this fly mainly in a French/Czech nymphing setup, but you can also fish it the old fashion way, on a dead upstream drift.