Warburton Tenor Backbore 1 ST large
                                
                                
                             
                            
                         
                            
                            
                        Warburton Tenor Backbore 1 ST large, Backbore for Tenor Trombone, Symphony tenor, With large shank, Standard model, Ø 6.76 mm bore, Silver-plated, There are three sizes of the ST backbore, numbered from 1-3, with 1 being the smallest and 3 being the largest