In our world, getting a flat front tire is not fun. That's why all our heavy-duty mowers have large, flat-free casters with deep-groove ball bearings and bearing caps. The tires are molded rubber with a small, hollow section to soften the ride. The large, well-sealed, deep-grove bearings don't require maintenance and almost always outlast the tire. The bearing caps keep twine and landscape flags from getting wrapped around the axle and damaging the bearings. Walk behinds use flat-free tires mounted on caged roller bearings and the Stander B™ uses pneumatic tires on sealed ball bearings.