The phrase "additional kit" refers to extra tools, equipment, or accessories that are added to something to enhance its functionality or performance. Full definition
But, it might take more time to get additional kits, the news service said. (health.com)
Most models require that you purchase additional kits or hardware to install them in these areas safely. (wetheparents.org)
It's a big difference, but the turbocharged engine of the GLX is an altogether more sophisticated set - up, and the flagship model also features a lot of additional kit for the money. (motoring.com.au)