Walker Mower MS Series Parts. Parts for Walker MS, S14 and S18 Mowers. The S series built on the smaller Model S platform and Walker’s patented Grass Handling System with Thru-Shaft PTO. It is faster and more powerful, and with reduced weight, the MS is designed to be productive and efficient. Able to run 36 to 56 inch decks, the new S series is the perfect choice for residential properties, gated yards, or demanding customers. Always Save on Walker Mower parts with ProParts Direct.