MTD 634-04237A  Caster Wheel Assembly

Wheels are used on all Stand-On, Riding, and Walk-Behind outdoor power equipment. Plastic wheels can wear down or break over time with impact, weight, and use. They can include wheels for the model itself, either 2-wheel or 4-wheel, or refer to the turning wheels for mower decks, like from a Zero-Turn's pivoting front wheels, or other attachments. While many wheels can be universal for certain push models, many larger push and riding equipment may require specific design and size to support more weight.