These 72mm Gecko™ Wheels are constructed of high-grip silicone rubber that offers excellent traction against a multitude of surfaces. The spoke design allows the wheels to compress and conform around objects with ease. The wheels are non-directional which means that they will provide the same reliable results no matter which direction you spin them. The plastic offset center core allows you to adjust your wheel location by flipping it around. One side has 8mm of drop to perfectly nestle a Sonic Hub in while the other is 12mm deep. The grippy surface and compliant design make this wheel is the perfect finishing touch to your goBILDA intake assembly.