This add-on set is for the 74920 railroad grade crossings for C Track. It is required for each additional parallel track. Contact track set: 3 straight tracks each 94.2 mm / 3-3/4". No other connections required. The road section can be adjusted for a spacing of 26 to 61 mm / 1" to 2-3/8" (track spacing of 66 to 101 mm / 2-5/8" to 4".