88.9mm (3.5") x 33mm Low Bounce PVC Wheels for 4mm Axle (2 pack) from Du-Bro - DUB350R
Takes a 5\/32 Axle (4mm). Du-Bro's low bounce captive air wheels have flown on more airplanes over the years than any other wheels on the market!  The wall thickness is consistent throughout the wheel giving you a balanced tire.  Comes complete with a sporty nylon metallic hub.  Works well on grass and paved runways.
Features:

Low-Bounce
Non-Treaded Rubber Tires
Nylon Hub for Longer Wear

 
  WARNING: This product can expose you to Diisononyl phthalate (DINP), which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov.