Jay always performs with the Vernet brand of thumb tip. It's considered to be the BEST QUALITY thumb tip available on the market!
This is the 'Regular' size. So unless you have HUGE hands (or really TINY hands) this will be the perfect size for you.
Definitely check out Jay's 'HUNDRED DOLLAR MIRACLES' DVD. It features 30 jaw-dropping tricks with the legendary Kowslowski thumb tip 'bill switch!'