VLS stands for vertical launch system. It is the main bolo indirect weapon system. The system is basically a mobile missile launcher. It was first equipped to the bolo mark three and from there, it vastly evolved. The mark threes VLS consisted of 60 non reloadable cells. By the bolo mark 19, there were many reloadable, magazine fed cells. The term light or heavy was decided by how many cells and magazine capacity, not the size of the missiles launched.