Loose Lug Nut Indicators, also know as Wheel Nut Indicators are a small piece of plastic that is injection molded with 24 teeth on them allowing them to be adjusted in to a circular pattern around a truck's hub. The purpose of these indicators are to show the operator that the truck (or trailer's) lug nuts have not rotated which would be a sign of loosening, causing an unsafe situation where a wheel could come loose, possibly injuring people or property.

The 24 points of the indicator are interference fit (an engineers way of saying pressed on) over the lug nut's hex head. They are tight enough to stay on in any weather but also not so tight that you can not remove or install by hand. The typical installation is with the indicators pointing in a clockwise direction, this way when/if a lug nut does happen to come loose the indicators rotate towards the outside of the wheel creating a larger pattern that is more easily visible to the vehicle operator. 

33mm Torque-Tight indicators are a very common size, in fact, they are so common that we sell 7 times the quantity of all other sizes combined!  Why is that? Well, 33mm (or 1-5/16" for us Imperial folks) is the size lug nut that is used on just about every heavy truck and trailer on the road in the United States, Canada, and Mexico. Now, there is a little more to the size than you might think. The 33mm dimension is the measurement across the flats on the hex head of the nut.  These lug nuts actually fit on to a m22x1.5 stud which commonly confuses some people in to ordering 22mm indicators when they actually need a 33mm.  The easiest way of knowing is simply by taking out a socket and seeing what fits, sockets (and wrenches) are sized the exact way that our indicators are. If you use a 33mm or 1-5/16" socket on the lug nuts then you know you're in the correct spot!