Sledges were manufactured by the French and supplied to all units - Schneider, Saint-Chamond, and Renault. They carried either fuel, ammunition, or a mixed load of fuel, ammo, rations, and water, plus tools and so on for maintenance.
They put a great strain on the Tanks, especially the clutch of the Renault, so a wheeled trailer was proposed but it didn't enter service until after the War.
Haven't got any dimensions, but the enclosed might help (maybe also with the British ones).
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