Further to Michael T's post, tinplate track sizes differ from one manufacturer to the next.
For those using O27 height wider radius track, even small differences can have one scratching their head when things just don't seem to line up. So you don't go nuts:
When using O54's, please note that the K-line version is 1/4 inch longer than Lionel's.
When using O42's , please note that the K-line version is 1/2 inch longer than Lionel's. Also K-line's O42 track has 5 ties, Lionel's have 3.
