The Xl is another version and it comes in two versions both diesels although I think Matt would build a gas one if you wanted. The standard XL is like the normal turbo diesel Ox. The GT version uses a larger hydraulic pump and larger hydraulic motors. The Gt version also has 1.5" axles standard. It is available with power steering or joy stick control. It also allows for auxiliary hydraulic circuits to be added easily. The Xl adds significantly to the water carrying capacity to the tune of about 600# additional I think. It also has more clearance for bigger tires and increased track clearance. A 14 gallon gas tank is standard and increased leg room. There are lots of little improvements and refinements also.