Dubro 1-3/4" Treaded Wheels (2) These wheels takes a 1/8 Axle (3mm). 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 & paved runways.