We used to send this out with every set of alloy wheels that we sold—because all of our aftermarket lug bolts were outfitted with 17mm heads, and this adapter was necessary to mate with the 19mm lug wrench in your jack kit. NO LONGER! All of our new aftermarket bolts have the proper 19mm head. If, however, you've lost your original adapter and need another, this is the one for you.