While the Mark XVI was more agile and easier to deploy than the Mark XVII , it proved less popular in combat than its companion mark because of its lighter offensive power. The Mark XVIII replaced both the XVI and XVII in relatively short order as the new 'standard' Bolo in an attempt to combine the best features of both its immediate predecessors. As usual, the new vehicle went up in size and weight (late-model Mark XVIIIs approached 10,000 tons), and space-to-ground deployment became a problem. Main armament was the Mark XVII's 60cm Hellbore, but the infinite repeaters were reduced to twelve with the deletion of the bow battery (which had been found to compromise the structural integrity of the glacis plate). The Mark XVIII adopted a 'sandwiched' hull: an outer ablative hull, then a thin