55n3 allows the logging and mining aficionado options. The Tichy Trucks with 36" HO wheels become REAL narrow gauge trucks, 3-1/2' wheelbase trucks with 23" wheels. The Bachmann log cars fit right in as do the the Tichy Ore cars. All the Tichy Ore cars need is one trussrod removed and a 1/16" wide strip added to the frame to be 55n3.