All my strollers have 16" wheels, but the smaller size wheels are 12" and it can be tricky fitting a pump in there to add air.
If you have an air compressor, that will work because of the small head. Alternatively, strollers such as Valco and Phi and Ted use inner tubes in their tires with bent valves. This allows you to use a regular hand pump. It can be hard to find these replacement tubes, however. Best bet: Amazon.com.