As part of Peter Drummond's 1901 classification scheme they became class F. They featured 6-feet 3½-inch driving wheels and weighed 41 long tons (42 t; 46 short tons).

The original batch had boilers pressed to 140 pounds-force per square inch (970 kPa), the later batch had slightly smaller boilers but a higher pressure of 150 lbf/in2 (1,030 kPa).

Of typical Allan/Jones appearance, they had outside cylinders of 18 by 24 inches (457 by 610 mm).

Withdrawal commenced in 1907, and by 1909 all-but-one of the Dübs-built examples had been withdrawn.

The remaining five survived until 1923 but none of them acquired a new London, Midland and Scottish Railway number.