When we developed the Wright WSZK61S61E8E-49S 61" Stander® ZK Mower with Briggs & Stratton 61E8E 37HP, nothing was held back! The result is the most productive and versatile large frame mower ever built. Big bore EFI engines provide power without compromising efficiency. High flow hydraulics propel high traction 23'' or 24'' tires for excellent hill holding, and dual sided fuel tanks provide all-day run time. Take on your next season with a ZK. It's the ultimate stand on mower. Period.