How to choose your inner tube
Check all the information indicated on the sidewall of the tyre (diameter and width). For example, 27.5 x 1.90 means a tyre with a 27.5-inch diameter that is 1.90 inches wide.
On the tyre sidewall you will also find the dimensions in mm in ETRTO international units.
For example, 50-584 means your tyre is 50mm wide with an inner diameter of 584 mm (27.5 x 2.00).