This boot is a direct replacement for the factory rubber boot shifter tunnel sealing boot.
This will provide a complete seal around the shifter handle, which when using the factory boot the hole is too large and will let noise, and fumes into the car.
The factory boot also has a very thick lower seal which can get in the way of the shifter assembly itself, so this boot eliminates that as well. All around this is the best solution for manual supra owners who are converting to the T56 or other transmissions where they do not have the giant shifter handle (reverse lockout mechanism) coming through the boot.