From their website:
Gun carriage based on lengthened APC chassis, which like the APC can operate in road mode or can retract its wheels and go into anti-grav mode. The model can be depicted in either mode and comes with an optional flight base. It comes with three different weapons options, one of which may be used with each kit. If swappability of weapons load is preferred, additional gun cradles and pins are available separately. It’s the perfect weapons accompaniment to the APC, or can operate in stand-alone batteries.