The T4 is the most popular choice from the Tourbillon series.  It features 4 holes for extra airflow and an extra thick 3/16 inch polished quartz disk on the bottom. 

25mm Quartz Bucket

-Features 4 holes drilled at an angle, so when you cover the top, air spins inside the bucket. Great for spinning beads.

-2.5mm wall thickness

-25mm OD, 20mm ID

-Slight bevel to ensure a marble seals it without thinning the rim