Lexus RX 450h 2012 Owner's Manual page 307

2-5. Driving information
Selecting trailer ball
Use the correct trailer ball for your application.
306
Trailer ball load rating
Matches or exceeds the gross
trailer weight rating of the trailer.
Ball diameter
Matches the size of the trailer cou-
pler. Most couplers are stamped
with the required trailer ball size.
Typical trailer ball
Trailer class
size
IV
II and III
I
Shank length
Protrudes beyond the bottom of
the lock washer and nut by at least
2 threads.
Shank diameter
Matches the ball mount hole diam-
eter size.
2 5/16 in.
2 in.
1 7/8 in.