Profi II harnesses feature a 2-inch lap belt which is safer and more comfortable than a 3-inch lap belt.
Profi II ASM belts feature the safer and more comfortable 2-inch lap belt, but are designed to be used as a four point belt with no Anti-sub strap. The Anti-Submarining technology is built into the shoulder belts.
Profi II-Y belts feature a double shoulder setup, one set of shoulder belts goes over your shoulders, and the second set over your HNR. This gives you the best solution available today.