An essential practice aid, the mouthpiece rim is a tool to achieve consistent elegance and efficiency to your tone and articulation.  A clear vocal tone on the rim will INSTANTLY clean up your sound and articulation on the trombone.  Use it as a superior solution whenever you would choose to buzz the mouthpiece in your practice.  

The Griego Oft 5 has a diameter of 1.004 which is similar to a Bach 5G