2011 Toyota RAV4 Owners Manual - Page 241

2-5. Driving information Selecting a trailer ball Use the correct trailer ball for your application. Trailer ball load rating Matches or exceeds the gross trailer weight rating of the trailer. Ball diameter Matches the size of the trailer coupler. Most couplers are stamped with the required trailer ball size. Trailer class Typical trailer ball size 2 When driving IV 2 5/16 in. II and III 2 in. I 1 7/8 in. Shank length Protrudes beyond the bottom of the lock washer and nut at least 2 threads. Shank diameter Matches the ball mount hole diameter size. 217