Exmark TTX650EKC604N0 60" Turf Tracer X-Series 21HP with Kohler ECV650 and UltraCut Series 4 Deck By virtually any measure, the Turf Tracer X-Series represents the definitive, full-featured hydro mower. Whether you choose the 52- or 60-inch cutting deck, the UltraCut™ Series 4 with splined spindle blade driver is up to the toughest jobs. As are the X-Series engines—Kohler® EFI. Ground speeds up to 6.75 mph, and up to 2.25 in reverse, also rank the Turf Tracer X-Series among the most productive mowers in its class.