The Southern Railway-built batches had a narrow footplate due to the width-restricted Hastings Line between Tonbridge and Hastings but these were never used on this duty and the cab was widened to on the British Railways batch. The tenders of Nos. 21C166–21C170 were fitted with TIA ("Traitement Integral Armand") chemical feed-water equipment that precipitated scale-forming constituents in the hard water of southern England into a non-adhesive mud that could be cleared using a manual "blow-down" valve. This equipment was retrospectively fitted to earlier members of the class. In 1948 the tender design was enlarged to provide a water capacity of .