Troy-Bilt TRBN31A-2M5GB66 123cc 4-Cycle Single Stage 21 in. Gas Snow Blower NewTroy-Bilt 123cc 4-Cycle Single Stage 21 in. 123cc 4-Cycle Single Stage 21 in. Snow Blower – 31A-2M5GB66. Troy-Bilt certified 123cc Pull-start 4-Cycle engine eliminates the need to mix oil and gas. High-performance auger design grips ground for maximum clearing power. Compact size for.