This set consists of a pair of 12' wheelbase 21'6" OHS chassis with cutouts in the headstock to fit the projecting stanchions on the bottom of the non-door end of the British Railways rivetted 21t end-tipping mineral wagon bodies (sold separately). These chassis should accept N-gauge or 2mm FS wheels on axles 14.8mm over pinpoints. Be careful fitting these, not to break the axleguards. Lifting N-gauge couplings are included (2 spare) which, when freed from the cage, may need careful cleaning in warm soapy water to free their movement. They can be slid into slots behind the headstocks, kept in place using soft glue, and sprung to return to the flat position with a shim of thin flexible plastic fed into the slot above the arm. Alternatively, a straight piece of fine flexible wire the right length, planted between the holes in the backs of the lifting arms, may keep them in place and also spring them to return flat after lifting.