The wire has been selected to be the same diameter as the the water/vacuum/steam pipes typically found on the prototype. Make a mark on the plugs and sockets so you always connect them the right way round (yes, we could have given you four different colours, but then you’d have to paint them).
For DCC locos, use when the decoder and motor are in different bodies. If the decoder and motor are in the same body, use LS24 instead.
A pack contains double the components shown in the photo.