I never liked how the Probuilder space rover front portion only had two wheels. It wouldn’t be able to move without the trailer, which didn’t make sense to me. I bought a second set with the intention of making the rover itself 4-wheeled and thus be trailer-free if so desired.
Each side now has a flip-down door. It can also now hold 4 passengers instead of 2.
Each side now has a flip-down door. It can also now hold 4 passengers instead of 2.