The Metropolitan Railway bought six kits for conversion to the Metropolitan Railway K Class 2-6-4T tank engines, which were similar in outline to the SECR K class. The remaining 17 complete kits at Woolwich were bought by the Southern Railway, and formed the basis of later locomotive classes such as the three-cylinder SR W class 2-6-4 tank locomotive. The prototype W class was produced in 1932 from N class parts with the addition of water tanks, a coal bunker, a rear bogie and a third cylinder between the frames. Woolwich also stocked a surplus of N class bogie components, and these were bought by the Southern for rebuilding the LB&SCR E1 class 0-6-0 tanks into the E1R class 0-6-2 tanks.