This is the 1/144 RX-77-2 Guncannon, Hayato's version from 109.
The basic construction is the same as Kai's version.
To differentiate it a little, the exhaust heat duct on the backpack is round for the 108 and hexagonal for the 109, as per the kit.
It's basically like comparing the early and late models.
The antennas are also divided into two shapes: conical and triangular.

1/144 RX-77-2 Guncannon 109 Hayato Kobayashi Machine | 八丸's Gunpla works