All of the MG 'Endless Waltz' kits are Katoki redesigns of the originals, they are solid builds and this one is no different. The articulation is not as advanced as kits from other lines (due to the 'Wing' Gundams being a little bit smaller/more stocky), but they can all strike a pose quite well.
Heavyarms features a bunch of hatches that open to reveal rocket pods everywhere (legs, front/side skirts, shoulders), as well as gatling guns within its chest.
It carries a massive belt-fed mini/gatling gun in its left hand, which is quite heavy and requires a bit of posing for the arm not to droop. The gun can be stored on the back.
There is a massive folding combat blade on its right arm.
As a neat little gimmick, an alternate left arm is also included, to enable you to recreate a scene from the TV show, where Heavyarms (piloted by Heero Yuy) drops its gatling gun and reveals a beam saber inside.
The kit is also available in 'Igel' or 'Custom' P-Bandai versions, the former including even more rockets/ankle treads and the latter in a different color scheme and other gatlings, so be sure to check out the different versions. This one is considered the base model.