101.6mm (4") x 38mm Big Inflatable Rubber Wheels for 4mm Axle (2 Pack) from Du-Bro - 400RV
Smooth inflatable tires with positive seal air valves. Features two piece bolt together hubs and hub caps. Wheels can be inflated (or deflated) thru a tiny valve in the side of the tire.
Note:  These wheels will not fit nor work for a beach cart or wheel chair.  
Includes:

2 Du-Bro Big Inflatable Wheels 4"


 
  WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm.  For more information go to www.P65Warnings.ca.gov.