Tracks are sold in sizes called "codes," which indicate the rail height in thousandths of an inch.
Examples: Code 100 (.100"), code 83 (.083"), and code 70 (.070") are common sizes in HO scale while code 80, code 70, and code 55 are used for N scale. These sizes represent the various sizes real railroads use.
Code 55Â has a rail height of .055", all products in this category will work in a code 55 model railway.