I forget which class hitch comes on our T4R as OEM, but here is some info which might help you. Taken from:
http://hitches4less.com/trailer-hitch-classes.html
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Class I Hitches
This is the lightest type of trailer hitch. A Class 1 trailer hitch can handle a gross trailer weight (GTW) of up to 2,000 lbs., and a maximum tongue weight of 200 lbs. The hitch may be a simple drawbar-type hitch or step bumper-type hitch. Other hitches may have a crossbar with a small one-inch or 1-1/2-inch square receiver, or a small 2-inch by 5/8-inch receiver. This type of hitch is often used on smaller cars, smaller pickups and smaller vans (minivans) for bicycle racks, camping racks, and light-duty towing. We sell many fine class 1 hitches as well as an economical, easy to install (do-it-yourself) Class 1 trailer hitch.
Class II Hitches
Class II hitches are for loads of up to 3,500 lbs. GTW and 300 lbs. tongue weight such as a small boat trailer, snowmobile trailer, motorcycle trailer or camper. This type of trailer hitch is appropriate for larger cars, full-size vans, full-size pickups and SUVs. Many of our class II hitches are designed specifically for your vehicle, and we have some universal class II trailer hitches as well.
Class III Hitches
Class III hitches can handle up to 5,000 lbs. GTW and 500 lbs. tongue weight. This type of hitch generally has a 2-inch rectangular receiver and is considered the "standard" type of hitch for general towing. Most of our class III hitches are designed specifically for your vehicle. There are also some universal-fit class III trailer hitches available.
Class IV Hitches
Class IV hitches are for up to 10,000 lbs. GTW and 1,000 to 1,200 lbs. of tongue weight. This type of hitch is usually a weight-distributing hitch. We carry many fine class IV hitches that are designed specifically for your vehicle.
Class V Hitches
Class V hitches are for extra heavy loads greater than 10,000 lbs. GTW and more than 1,200 lbs. tongue weight. This type of hitch is usually a weight-distributing hitch. This type of hitch may have up to a 2-1/2 inch receiver with a 3/4-inch pinhole. Typical uses might be to tow a car trailer, horse trailer or unusually large boat or camper.