Port Tube 2-1/2" ID Adjustable

Good port for the money but the inner diameter of the smaller tube is 2.6 inches, bigger than what's stated. This will change the length you calculated and potentially make this tube unusable for you if you were banking on using it at its maximum extension.

It may also be a good idea to mount the tube outside the speaker box when fine tuning the length so it's easier to adjust. Just something to keep in mind.

The ID of this tube is 2 5/8". It's a little bigger than the published size.