R-454B

A2L low-GWP refrigerant blend (GWP ~466 vs. R-410A's 2,088). One of the two primary replacements for R-410A in new residential AC and heat-pump systems under the 2025 EPA AIM Act phasedown; the other is R-32. Mildly flammable — service requires A2L-rated tools and updated EPA 608 certification.