2.50-4 wheels are commonly used as caster wheels on utility carts, small hand trucks, and other utility equipment. They are also used on some small to medium sized mobility scooters.
2.50-4 wheels can be pneumatic or solid:
Pneumatic
These wheels are air-filled and can be used in a variety of environments, including hospitals, outdoor equipment, and hotel-motel carts. They are compatible with a 4" rim and require an inner tube.
Solid
These wheels are durable and can perform well on terrains where pneumatic tires can't. They have more structural integrity than pneumatic tires and won't go flat or deform. Some solid 2.50-4 wheels are made with premium steel rims for heavy-duty workloads.