The O Series will tend towards being more free, while retaining the ability to sing with the head voice. With the O series has the ability to play with both head and chest playing, but the color, and weight of sound is more towards a blending darker sound, when pushed the O series is still alive and clear.
The mouthpieces designed in this series are deeper than the V series which are designed to be a solo mouthpiece. The O stands for Orchestral and will provide you with a deeper voice, richer sound, more weight of sound, and a sound that will blend easier with your colleagues.
The below S series pieces are listed in order from largest to smallest cup diameter.
This is the monster of the series, and is designed for those people that want to throw air through their equipment. This has a tremendous weight of sound and I would recommend it to either those with very developed embouchures or those who are exclusively second trombone players. Despite that, it will still work admirably over the entire register.
Perhaps the slightly smaller feel than traditional four's, I find this a good balance between weight of sound and technical fluency. Whereas traditional fours tend to be difficult in the high register in regards to clarity. This mouthpiece sings effortlessly all the way into the upper register.
"The Classic". A perfect middle of the road mouthpiece that without compromising quality will allow you to cross styles effortlessly. Unlike previous fives this mouthpiece is acoustically perfect across every register, and I would particularly recommend this for those who developing their basic technique as well as the hard accomplished professional.