We've just started shipping TLR338002 which is the 22-4 Shorty Pack Conversion chassis. We've had a few people ask, "What's that little black part for?" I just wanted to help clear the air and give the detailed info on why we made it.
The right side battery strap on the 22-4 actually works as the body mount as well, to hold the body up on the right side. Since the right side battery strap is not used when running the shorty conversion chassis, we designed and made a tube that slides over the body post that basically acts as the body mount portion of the right side battery strap to support the right rear of the body. See the image below. Just slide the body clip through the lower hole as normal to hold the battery strap, and it will hold the body mount in place just the same.
I hope that makes it clear why this part in included, and now it can be installed without issue!