Rotation is the whole point. A turning spit bastes the meat in its own rendered fat on every revolution, which is why rotisserie chicken has skin you cannot reproduce on a grate — and why the host gets to sit with the guests instead of standing over the fire turning things.
This kit adds that to the grill you already own. The frame mounts into the modular accessory system, the brackets are adjustable and are designed to take a rotisserie motor, and the stainless rod and four spikes hold the load centred and locked.
What's in the box

1 × mild steel frame, high-temperature painted
2 × grill mounts
2 × adjustable rotisserie motor / rod mounting brackets
1 × stainless steel rod
4 × stainless steel rotisserie spikes

The rotisserie motor is not included — the brackets are built to accept one.
What you'll cook: whole chickens, a leg or shoulder of lamb, pork loin, a shawarma stack, or a bone-in ribeye big enough to argue over.
Fits: The Mini, The Tejano and The Reaper, via the modular accessory mounts.
Bank your fire to the sides, not underneath. Rotisserie wants indirect heat — fat dripping onto coals directly below the meat is how you get flare-ups instead of dinner.