Discontinued long ago by Nissan, then again by the previous reproduction manufacturer around a decade ago, these are the ducts that direct fresh air from in front of the core support to the inner fender. That air then supplies the ventilation system of your 240Z. Most of these you find have long since begun to fall apart. This kit is a very good reproduction of the original left and right piece. They are made of high quality, thick, flexible plastic, and include the metal attachment bracket at the inner fender, along with the inner support to keep the opening at the right shape. Includes attachment screws.
Just like the original boots, these reproductions are a very tight fit. Warming up the new boots will make installation much easier (we recommend letting them sit in the sun for a while). A lubricant may also come in handy as well, but is not required.