For a cheap kit, this GVT wagon is very well specified. When it came time to fit the underframe bits, which are mostly from glass-reinforced plastic, I find that this is no simple 4-wheel wagon.
A rocking, or compensated, axle is provided. This should aid road-holding over uneven trackwork. Something narrow gauge lines are notorious for. On a wagon with this short a wheelbase, I wonder if it's strictly speaking necessary, but a nice touch from the manufacturer.