Apparently all three initially had solid cast iron wheels with iron tyres but one was altered in the 1880's to have the outer wheels spoked with the inner pair solid. I cannot find an explanation for the solid wheels: none of the other Highland locomotives had these. However they may look in retrospect the wheels must have proved to be satisfactory in service as all three survived to LMS days solid wheels and all and all received LMS numbers and livery before being withdrawn between 1928 and 1932. The LMS seemed to have been confused by them as well, one was numbered in with a Peter Drummond class of outside cylinder 0-6-0T's and given the power classification of 2F instead of a nominal 0P! The RCTS book on the Highland describes them as 'remarkable for their longevity, a tribute to their good design, sound construction and usefulness' which is as good an epitaph as a class could have.