 The original slatted upper sides of the Type XD tender's coal bunker were soon replaced by sheet-metal sides to increase the coal capacity.From c. 1925, some Type XD tenders from Classes 6H, 6J and 8 were completely rebuilt by the SAR, by mounting a new upper structure on the existing underframe.Since their new tanks increased their water capacity to , these tenders were reclassified to Type XF.