A modular manifold system that allows multiple nozzles to be fitted to a single NPT port, with rotation clamping. The manifolds allow the Nozzle Tube System, Generic Nozzles and the Grind-Loc System to be grouped in front of the grinding wheel. The Donuts are slid over a cross-drilled ported tube of the desired length. 3/8” system donuts fit over 3/8” NPT ported tubes, 1/2” system donuts fit over 1/2” NPT ported tubes, and 3/4” system donuts fit over 3/4” NPT ported tubes. When fitting NPT male threads into the outlet of Active Donuts a locknut should be used to prevent excessive thread engagement from blocking the internal flow path. The Active Donut female thread is one size smaller than the ported tube diameter that it slides over.