49 C.F.R. § 213.349
Any mismatch of rails at joints may not be more than that prescribed by the following table—
| Class of track | Any mismatch of rails at joints may not be more than the following— | |
|---|---|---|
| On the tread of the rail ends (inch) | On the gage side of the rail ends (inch) | |
| Class 6, 7, 8 and 9 | 1⁄8 | 1⁄8 |