This is the Laskey Joseph Alessi model 55SOLO. Rim Inner Diameter: 25.5mm Cup Depth: Mid-Shallow Both the 55 and 60 models were designed under the supervision of Mr. Alessi himself, with his disciple Brian Wendel (principal trombonist of the Cleveland Orchestra) and Carlos Fernandez (principal trombonist of the New York City Ballet Orchestra) in charge of the design. The final specifications and measurements were approved by Mr. Alessi.