Question: what kind of tube do i need for my bike?
Answer: The size is almost always written somewhere on the sidewall of the tyre. Inner tubes typically state a wheel diameter and width range for which they will work, e.g. 26 x 1.95-2.125", indicating that the tube is intended to fit a 26 inch tyre with a width of between 1.95 inches and 2.125 inches.