That depends on what you are trying to adjust...
Height: No. The Durso Standpipe is fixed height. We have not seen a variable height aquarium so don't see the need for a variable height Durso Standpipe. If you purchase the Durso Standpipe from us you would specify the height you need during checkout. You can always trim the Durso Standpipe to be shorter with standard cutting tools such as a chop saw. If you are building your own, you may be able to find a telescoping coupling adapter which allows a few inches of height adjustment. This fitting is around $10 to $13.
Flow Rate: Generally Yes. The vent hole on the top of the Durso Standpipe is adjusted to match the flow rate of your tank. (Larger hole for lower flow rates). The Durso Standpipe does not increase or reduce your flow rate, you are adjusting the standpipe to work with your flow rate.