Our Speed-Wheels come with 8" swivel care-free (foam-filled) tires. The adapters are manufactured out of 1 5/8" (outside diameter) steel. These adapters accommodate all fittings for 1 1/4" pipe. These wheels are perfect for a quick Speed-Rail rig that requires movement or for creating your own rickshaw/Speed-Rail dolly. The Speed-Wheels feature a strong and durable locking mechanism, ensuring ease of use.