An ultrasonic instrument (120, 220, 320) comprising: an ultrasonic transducer; an acoustic waveguide (448, 548) in acoustic communication with the ultrasonic transducer, wherein the acoustic waveguide (448, 548) defines a longitudinal axis, wherein the acoustic waveguide (448, 548) comprises: a bore (482, 582) extending transversely through the acoustic waveguide (448, 548), an anchor pin (447, 547), wherein the anchor pin (447, 547) is insertable through the bore (482, 582) and is operable to secure the acoustic waveguide (448, 548) relative to the ultrasonic instrument, and an acoustic isolator (472, 572), wherein the acoustic isolator (472, 572) is angularly disposed about the acoustic waveguide (448, 548) and is operable to acoustically isolate the acoustic waveguide, wherein the acoustic isolator (472, 572) comprises a first opening (478, 578) extending through the acoustic isolator (472, 572), wherein the first opening (478, 578) is configured to receive the anchor pin (447, 547); and an ultrasonic blade (452, 552) in acoustic communication with the acoustic waveguide (448, 548) such that the ultrasonic transducer is operable to drive the ultrasonic blade (452, 552) to vibrate ultrasonically via the acoustic waveguide, characterised in that the first opening (478, 578) has a diameter greater is than or equal to the diameter of the bore (482, 582) of the acoustic waveguide (448, 548). an ultrasonic transducer; an acoustic waveguide (448, 548) in acoustic communication with the ultrasonic transducer, wherein the acoustic waveguide (448, 548) defines a longitudinal axis, wherein the acoustic waveguide (448, 548) comprises: a bore (482, 582) extending transversely through the acoustic waveguide (448, 548), an anchor pin (447, 547), wherein the anchor pin (447, 547) is insertable through the bore (482, 582) and is operable to secure the acoustic waveguide (448, 548) relative to the ultrasonic instrument, and an acoustic isolator (472, 572), wherein the acoustic isolator (472, 572) is angularly disposed about the acoustic waveguide (448, 548) and is operable to acoustically isolate the acoustic waveguide, wherein the acoustic isolator (472, 572) comprises a first opening (478, 578) extending through the acoustic isolator (472, 572), wherein the first opening (478, 578) is configured to receive the anchor pin (447, 547); and an ultrasonic blade (452, 552) in acoustic communication with the acoustic waveguide (448, 548) such that the ultrasonic transducer is operable to drive the ultrasonic blade (452, 552) to vibrate ultrasonically via the acoustic waveguide, characterised in that the first opening (478, 578) has a diameter greater is than or equal to the diameter of the bore (482, 582) of the acoustic waveguide (448, 548). a bore (482, 582) extending transversely through the acoustic waveguide (448, 548), an anchor pin (447, 547), wherein the anchor pin (447, 547) is insertable through the bore (482, 582) and is operable to secure the acoustic waveguide (448, 548) relative to the ultrasonic instrument, and an acoustic isolator (472, 572), wherein the acoustic isolator (472, 572) is angularly disposed about the acoustic waveguide (448, 548) and is operable to acoustically isolate the acoustic waveguide, wherein the acoustic isolator (472, 572) comprises a first opening (478, 578) extending through the acoustic isolator (472, 572), wherein the first opening (478, 578) is configured to receive the anchor pin (447, 547); and an ultrasonic blade (452, 552) in acoustic communication with the acoustic waveguide (448, 548) such that the ultrasonic transducer is operable to drive the ultrasonic blade (452, 552) to vibrate ultrasonically via the acoustic waveguide, characterised in that the first opening (478, 578) has a diameter greater is than or equal to the diameter of the bore (482, 582) of the acoustic waveguide (448, 548).