The Turbo Top was designed to give you 2 stages of airflow on the Tourbillon. One side completely seals the Tourbillon, and if you flip it over, the other side has 2 slits cut at diagonals to add airflow. 

Each Turbo Top comes in a custom made wood box.

The XL fits the 30mm quartz products, and is highly recommended for a great seal on Tourbillon XL's.