I got them at a chinese store about 2 decades ago. The back carton of the box showed 4 main models, of which I only got 3, the last one being a black one that never came to the stores
Each set came with a main robot and a driller vehicle, with varied colors in their armor, weaponry and pilots (small metallic figures that could be inserted into both the robot and drillers)
Some came with unique pieces, like rubber hoses, sniper arm cannons with individual pilots for them, etc
All of the pieces were interchangeable, allowing for strange combinations, one could even attach a driller to a robot as an arm.
Dont remember their name, sadly, so i come to the experts on the field.http://i39.tinypic.com/s15n3o.jpg