Small adjustable telescopic reflex port.
These are an excellent item for fine tuning speaker cabinets & allowing you to achieve a tailored bass response to your personal liking; they are also very handy for experimentation when finalising designs or replacing bass units.
These telescopic ports are simple to install & use, an essential item for the loudspeaker hobbyist or builder:
Tube bore: 35mm
Outside diameter: 45mm
Adjustment range: 110-210mm
Flange diameter: 65mm
Cross section area (SV ): 9.6cm squared