Romera Brass Mouthpiece "Model Omi" Signature model of Mr. Akinori Takahashi, Principal Horn of the Tokyo Philharmonic Orchestra. This is a perfect mouthpiece with a balanced design, paying close attention to rim shape, weight, and other details! A3R (for low register) Inner diameter 17.50mm The "Model Omi" mouthpiece I've been searching for. The A3R excels in the balance of a deep tone and resistance in the mid-low range.