Caster; Rigid; 6"x2"; Flat Free; Plate (4x4-1/2; holes: 2-5/8x3-5/8 slotted to 3x3); Prec BB; 250#; Sawtooth Tread; Premium Hub (Swivel is #66706) (Trio Pines 6660R-01-AFR)
Flat Free (also known as semi-pneumatic) are extremely popular wheels. Made to perform like a pneumatic tire, they are filled with a lightweight, microcellular polyurethane foam. They retain the lightweight, bounce and cushion like a pneumatic tire, without the nuisance of air leaks.
NOTE: Flat free wheels occasionally experience temporary flat-spotting even when loaded within the acceptable weight limits. Flat-spotting is impacted by environmental factors, such as warmer conditions. It will dissipate after a few minutes of rolling, depending on the size and duration of the standing load. This is a normal occurrence of these wheels and is not a product failure. If your application cannot tolerate this temporary condition, another material type may be preferable.
Please note that storing these wheels in areas that are subject to extreme temperature fluctuations can destroy the microcellular foam interior.