Weril GG292L Gagliardi II Professional Bass Trombone Closeout The GG292L features a .562-inch bore with an independent double rotor design in Bb / F/ Gb / D plus 3 interchangable mouthpipes to customize the reponse of the instrument to the player. The GG292L also features a 9.5-inch gold brass bell and open wrap design for outstanding resonance and response.