heres the description straight from parts express
The unique flared-end construction of the Precision Port™ system enables it to outperform any standard port tube on the market. Conventional tubes suffer from nasty turbulence at the entrance and exit of the port, producing unwanted noise and poor sound quality. The Precision Port™ system overcomes these problems and as a result can actually produce a gain of up to 3 dB in output! Now you can experience good looks, low distortion, and superior overall sound quality thanks to the Precision Port™ system. Convenient front screw holes make this tube easier to install than others on the market. Create a port up to 17" long, then glue with PVC glue found at any plumbing supply house. Installation instructions included. Dimensions: • 7-1/4" outside flare outer diameter • 6-1/4" cutout • 6-3/16" inside flare outer diameter. Also available in 2", 3", and 6" diameters.
